feat!: enforce required MCP spec fields in McpSchema; lenient wire deserialization (#928)

Every wire-serialized record in McpSchema now validates spec-required
fields at construction time. Wire deserialization is intentionally
lenient: a missing required field is replaced with a documented default
and a WARN is logged, instead of failing the parse. A required-first
builder convention is introduced across the schema so it is no longer
possible to obtain a builder that is missing required state.

Required-field guards
---------------------
Every wire record's compact constructor asserts non-null (and non-empty
for String identifiers like name, uri, uriTemplate, version) on its
spec-required components. Passing null now throws
IllegalArgumentException at construction time instead of silently
producing invalid JSON via @JsonInclude(NON_ABSENT). This applies to
the JSON-RPC envelopes, lifecycle types, resource/prompt/tool requests
and results, sampling and elicitation, content records, root, complete,
logging and progress notifications, and the two CompleteReference
implementations. See MIGRATION-2.0.md for the full list.

Lenient wire deserialization
----------------------------
For each of those records (except JSONRPCResponse.JSONRPCError, which
still fails fast) a @JsonCreator static `fromJson` factory substitutes
a documented default for any absent required field — "" for strings,
[] for collections, {} for maps, 0 / 0.0 for numerics, INFO for
LoggingLevel, USER for SamplingMessage.role, ASSISTANT for
CreateMessageResult.role, CANCEL for ElicitResult.action, {values=[]}
for CompleteResult.completion — and logs a WARN naming the field and
the value used. Application code can still observe a malformed message
and react, but the SDK no longer halts the conversation.

Builder convention
------------------
Records that have a builder gain a required-first factory method
`builder(req1, req2, …)`; setters for required fields are removed from
the builder so it cannot be left in an invalid state. Existing no-arg
`builder()` factories and required-field setters are kept where source
compatibility demands it but are marked @Deprecated. New builders are
also added for several records that previously had none (ProgressNotification,
JSONRPCError, CompleteRequest, list/result types, content records, ...).

JSON-RPC envelope ergonomics
----------------------------
Previously every JSON-RPC envelope had to be constructed via the
canonical record constructor and the literal "2.0" string had to be
threaded through every call site, e.g.

    new JSONRPCRequest("2.0", "tools/call", id, params)
    new JSONRPCResponse("2.0", id, result, null)
    new JSONRPCResponse("2.0", id, null, new JSONRPCError(code, message, null))

Now:

    new JSONRPCRequest("tools/call", id, params)              // jsonrpc defaulted
    new JSONRPCNotification("notifications/initialized")       // params optional
    JSONRPCResponse.result(id, result)                        // factory
    JSONRPCResponse.error(id, new JSONRPCError(code, message)) // 2-arg error

JSONRPCResponse's compact constructor additionally enforces the
JSON-RPC invariant that exactly one of `result` / `error` is set —
previously the SDK could build envelopes that violated the protocol.

CompleteReference changes
-------------------------
- PromptReference.equals/hashCode now key on `name` only (previously
  derived from identifier()+type()). Two refs with the same name but
  different titles now compare equal — code using PromptReference as a
  map/set key should be audited.
- PromptReference's compact constructor pins `type` to "ref/prompt"
  and logs a WARN if the caller supplies a different non-null value.
  The legacy two-arg `PromptReference(String type, String name)`
  constructor remains @Deprecated.
- ResourceReference's record components are reduced from (type, uri)
  to (uri) — positional construction breaks. The legacy
  `ResourceReference(String type, String uri)` constructor stays
  @Deprecated and ignores `type`.
- CompleteReference.identifier() is @Deprecated and now returns null
  via a default method on the interface.

Tests / refactor
----------------
Conformance harness, integration tests, sample apps, and internal
callers were migrated to the new builder factories and convenience
constructors. No semantic changes to client/server runtime behaviour
beyond the McpSchema changes above.

Docs
----
- MIGRATION-2.0.md: required-field section now covers the broader
  record set and the lenient-deserialization behaviour; PromptReference
  WARN behaviour and ResourceReference component reduction are
  documented; the JSON-RPC envelope section is rewritten to compare the
  pre-2.0 surface with the new one.
- CONTRIBUTING.md: the "Evolving wire-serialized records" recipe is
  split into two cases — adding a new optional field (existing rules)
  and adding/maintaining a spec-required field (new rules covering
  Assert in compact constructor, @JsonCreator fromJson with defaults
  and WARN, required-first builder factory).

Signed-off-by: Dariusz Jędrzejczyk <2554306+chemicL@users.noreply.github.com>

mcp-test/src/test/java/io/modelcontextprotocol/client/McpAsyncClientResponseHandlerTests.java

@@ -30,7 +30,8 @@ import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 class McpAsyncClientResponseHandlerTests {
 
-	private static final McpSchema.Implementation SERVER_INFO = new McpSchema.Implementation("test-server", "1.0.0");
+	private static final McpSchema.Implementation SERVER_INFO = McpSchema.Implementation.builder("test-server", "1.0.0")
+		.build();
 
 	private static final McpSchema.ServerCapabilities SERVER_CAPABILITIES = McpSchema.ServerCapabilities.builder()
 		.tools(true)
@@ -43,13 +44,14 @@ class McpAsyncClientResponseHandlerTests {
 
 	private static MockMcpClientTransport initializationEnabledTransport(
 			McpSchema.ServerCapabilities mockServerCapabilities, McpSchema.Implementation mockServerInfo) {
-		McpSchema.InitializeResult mockInitResult = new McpSchema.InitializeResult(ProtocolVersions.MCP_2025_11_25,
-				mockServerCapabilities, mockServerInfo, "Test instructions");
+		McpSchema.InitializeResult mockInitResult = McpSchema.InitializeResult
+			.builder(ProtocolVersions.MCP_2025_11_25, mockServerCapabilities, mockServerInfo)
+			.instructions("Test instructions")
+			.build();
 
 		return new MockMcpClientTransport((t, message) -> {
 			if (message instanceof McpSchema.JSONRPCRequest r && METHOD_INITIALIZE.equals(r.method())) {
-				McpSchema.JSONRPCResponse initResponse = new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION,
-						r.id(), mockInitResult, null);
+				McpSchema.JSONRPCResponse initResponse = McpSchema.JSONRPCResponse.result(r.id(), mockInitResult);
 				t.simulateIncomingMessage(initResponse);
 			}
 		}).withProtocolVersion(ProtocolVersions.MCP_2025_11_25);
@@ -57,7 +59,7 @@ class McpAsyncClientResponseHandlerTests {
 
 	@Test
 	void testSuccessfulInitialization() {
-		McpSchema.Implementation serverInfo = new McpSchema.Implementation("mcp-test-server", "0.0.1");
+		McpSchema.Implementation serverInfo = McpSchema.Implementation.builder("mcp-test-server", "0.0.1").build();
 		McpSchema.ServerCapabilities serverCapabilities = McpSchema.ServerCapabilities.builder()
 			.tools(false)
 			.resources(true, true) // Enable both resources and resource templates
@@ -111,37 +113,37 @@ class McpAsyncClientResponseHandlerTests {
 
 		// Create a mock tools list that the server will return
 		Map<String, Object> inputSchema = Map.of("type", "object", "properties", Map.of(), "required", List.of());
-		McpSchema.Tool mockTool = McpSchema.Tool.builder()
-			.name("test-tool-1")
+		McpSchema.Tool mockTool = McpSchema.Tool
+			.builder("test-tool-1", JSON_MAPPER, JSON_MAPPER.writeValueAsString(inputSchema))
 			.description("Test Tool 1 Description")
-			.inputSchema(JSON_MAPPER, JSON_MAPPER.writeValueAsString(inputSchema))
 			.build();
 
 		// Create page 1 response with nextPageToken
 		String nextPageToken = "page2Token";
-		McpSchema.ListToolsResult mockToolsResult1 = new McpSchema.ListToolsResult(List.of(mockTool), nextPageToken);
+		McpSchema.ListToolsResult mockToolsResult1 = McpSchema.ListToolsResult.builder(List.of(mockTool))
+			.nextCursor(nextPageToken)
+			.build();
 
 		// Simulate server sending tools/list_changed notification
-		McpSchema.JSONRPCNotification notification = new McpSchema.JSONRPCNotification(McpSchema.JSONRPC_VERSION,
-				McpSchema.METHOD_NOTIFICATION_TOOLS_LIST_CHANGED, null);
+		McpSchema.JSONRPCNotification notification = new McpSchema.JSONRPCNotification(
+				McpSchema.METHOD_NOTIFICATION_TOOLS_LIST_CHANGED);
 		transport.simulateIncomingMessage(notification);
 
 		// Simulate server response to first tools/list request
 		McpSchema.JSONRPCRequest toolsListRequest1 = transport.getLastSentMessageAsRequest();
 		assertThat(toolsListRequest1.method()).isEqualTo(McpSchema.METHOD_TOOLS_LIST);
 
-		McpSchema.JSONRPCResponse toolsListResponse1 = new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION,
-				toolsListRequest1.id(), mockToolsResult1, null);
+		McpSchema.JSONRPCResponse toolsListResponse1 = McpSchema.JSONRPCResponse.result(toolsListRequest1.id(),
+				mockToolsResult1);
 		transport.simulateIncomingMessage(toolsListResponse1);
 
 		// Create mock tools for page 2
-		McpSchema.Tool mockTool2 = McpSchema.Tool.builder()
-			.name("test-tool-2")
+		McpSchema.Tool mockTool2 = McpSchema.Tool
+			.builder("test-tool-2", JSON_MAPPER, JSON_MAPPER.writeValueAsString(inputSchema))
 			.description("Test Tool 2 Description")
-			.inputSchema(JSON_MAPPER, JSON_MAPPER.writeValueAsString(inputSchema))
 			.build();
 		// Create page 2 response with no nextPageToken (last page)
-		McpSchema.ListToolsResult mockToolsResult2 = new McpSchema.ListToolsResult(List.of(mockTool2), null);
+		McpSchema.ListToolsResult mockToolsResult2 = McpSchema.ListToolsResult.builder(List.of(mockTool2)).build();
 
 		// Simulate server response to second tools/list request with page token
 		McpSchema.JSONRPCRequest toolsListRequest2 = transport.getLastSentMessageAsRequest();
@@ -152,8 +154,8 @@ class McpAsyncClientResponseHandlerTests {
 		assertThat(params).isNotNull();
 		assertThat(params.cursor()).isEqualTo(nextPageToken);
 
-		McpSchema.JSONRPCResponse toolsListResponse2 = new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION,
-				toolsListRequest2.id(), mockToolsResult2, null);
+		McpSchema.JSONRPCResponse toolsListResponse2 = McpSchema.JSONRPCResponse.result(toolsListRequest2.id(),
+				mockToolsResult2);
 		transport.simulateIncomingMessage(toolsListResponse2);
 
 		// Verify the consumer received all expected tools from both pages
@@ -171,14 +173,13 @@ class McpAsyncClientResponseHandlerTests {
 		MockMcpClientTransport transport = initializationEnabledTransport();
 
 		McpAsyncClient asyncMcpClient = McpClient.async(transport)
-			.roots(new Root("file:///test/path", "test-root"))
+			.roots(Root.builder("file:///test/path").name("test-root").build())
 			.build();
 
 		assertThat(asyncMcpClient.initialize().block()).isNotNull();
 
 		// Simulate incoming request
-		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION,
-				McpSchema.METHOD_ROOTS_LIST, "test-id", null);
+		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(McpSchema.METHOD_ROOTS_LIST, "test-id");
 		transport.simulateIncomingMessage(request);
 
 		// Verify response
@@ -187,8 +188,9 @@ class McpAsyncClientResponseHandlerTests {
 
 		McpSchema.JSONRPCResponse response = (McpSchema.JSONRPCResponse) sentMessage;
 		assertThat(response.id()).isEqualTo("test-id");
-		assertThat(response.result())
-			.isEqualTo(new McpSchema.ListRootsResult(List.of(new Root("file:///test/path", "test-root"))));
+		assertThat(response.result()).isEqualTo(McpSchema.ListRootsResult
+			.builder(List.of(McpSchema.Root.builder("file:///test/path").name("test-root").build()))
+			.build());
 		assertThat(response.error()).isNull();
 
 		asyncMcpClient.closeGracefully();
@@ -213,26 +215,24 @@ class McpAsyncClientResponseHandlerTests {
 		assertThat(asyncMcpClient.initialize().block()).isNotNull();
 
 		// Create a mock resources list that the server will return
-		McpSchema.Resource mockResource = McpSchema.Resource.builder()
-			.uri("test://resource")
-			.name("Test Resource")
+		McpSchema.Resource mockResource = McpSchema.Resource.builder("test://resource", "Test Resource")
 			.description("A test resource")
 			.mimeType("text/plain")
 			.build();
-		McpSchema.ListResourcesResult mockResourcesResult = new McpSchema.ListResourcesResult(List.of(mockResource),
-				null);
+		McpSchema.ListResourcesResult mockResourcesResult = McpSchema.ListResourcesResult.builder(List.of(mockResource))
+			.build();
 
 		// Simulate server sending resources/list_changed notification
-		McpSchema.JSONRPCNotification notification = new McpSchema.JSONRPCNotification(McpSchema.JSONRPC_VERSION,
-				McpSchema.METHOD_NOTIFICATION_RESOURCES_LIST_CHANGED, null);
+		McpSchema.JSONRPCNotification notification = new McpSchema.JSONRPCNotification(
+				McpSchema.METHOD_NOTIFICATION_RESOURCES_LIST_CHANGED);
 		transport.simulateIncomingMessage(notification);
 
 		// Simulate server response to resources/list request
 		McpSchema.JSONRPCRequest resourcesListRequest = transport.getLastSentMessageAsRequest();
 		assertThat(resourcesListRequest.method()).isEqualTo(McpSchema.METHOD_RESOURCES_LIST);
 
-		McpSchema.JSONRPCResponse resourcesListResponse = new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION,
-				resourcesListRequest.id(), mockResourcesResult, null);
+		McpSchema.JSONRPCResponse resourcesListResponse = McpSchema.JSONRPCResponse.result(resourcesListRequest.id(),
+				mockResourcesResult);
 		transport.simulateIncomingMessage(resourcesListResponse);
 
 		// Verify the consumer received the expected resources
@@ -261,21 +261,29 @@ class McpAsyncClientResponseHandlerTests {
 		assertThat(asyncMcpClient.initialize().block()).isNotNull();
 
 		// Create a mock prompts list that the server will return
-		McpSchema.Prompt mockPrompt = new McpSchema.Prompt("test-prompt", "Test Prompt", "Test Prompt Description",
-				List.of(new McpSchema.PromptArgument("arg1", "Test argument", "Test argument", true)));
-		McpSchema.ListPromptsResult mockPromptsResult = new McpSchema.ListPromptsResult(List.of(mockPrompt), null);
+		McpSchema.Prompt mockPrompt = McpSchema.Prompt.builder("test-prompt")
+			.title("Test Prompt")
+			.description("Test Prompt Description")
+			.arguments(List.of(McpSchema.PromptArgument.builder("arg1")
+				.title("Test argument")
+				.description("Test argument")
+				.required(true)
+				.build()))
+			.build();
+		McpSchema.ListPromptsResult mockPromptsResult = McpSchema.ListPromptsResult.builder(List.of(mockPrompt))
+			.build();
 
 		// Simulate server sending prompts/list_changed notification
-		McpSchema.JSONRPCNotification notification = new McpSchema.JSONRPCNotification(McpSchema.JSONRPC_VERSION,
-				McpSchema.METHOD_NOTIFICATION_PROMPTS_LIST_CHANGED, null);
+		McpSchema.JSONRPCNotification notification = new McpSchema.JSONRPCNotification(
+				McpSchema.METHOD_NOTIFICATION_PROMPTS_LIST_CHANGED);
 		transport.simulateIncomingMessage(notification);
 
 		// Simulate server response to prompts/list request
 		McpSchema.JSONRPCRequest promptsListRequest = transport.getLastSentMessageAsRequest();
 		assertThat(promptsListRequest.method()).isEqualTo(McpSchema.METHOD_PROMPT_LIST);
 
-		McpSchema.JSONRPCResponse promptsListResponse = new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION,
-				promptsListRequest.id(), mockPromptsResult, null);
+		McpSchema.JSONRPCResponse promptsListResponse = McpSchema.JSONRPCResponse.result(promptsListRequest.id(),
+				mockPromptsResult);
 		transport.simulateIncomingMessage(promptsListResponse);
 
 		// Verify the consumer received the expected prompts
@@ -295,8 +303,9 @@ class McpAsyncClientResponseHandlerTests {
 		// Create a test sampling handler that echoes back the input
 		Function<McpSchema.CreateMessageRequest, Mono<McpSchema.CreateMessageResult>> samplingHandler = request -> {
 			var content = request.messages().get(0).content();
-			return Mono.just(new McpSchema.CreateMessageResult(McpSchema.Role.ASSISTANT, content, "test-model",
-					McpSchema.CreateMessageResult.StopReason.END_TURN));
+			return Mono.just(McpSchema.CreateMessageResult.builder(McpSchema.Role.ASSISTANT, content, "test-model")
+				.stopReason(McpSchema.CreateMessageResult.StopReason.END_TURN)
+				.build());
 		};
 
 		// Create client with sampling capability and handler
@@ -308,18 +317,18 @@ class McpAsyncClientResponseHandlerTests {
 		assertThat(asyncMcpClient.initialize().block()).isNotNull();
 
 		// Create a mock create message request
-		var messageRequest = new McpSchema.CreateMessageRequest(
-				List.of(new McpSchema.SamplingMessage(McpSchema.Role.USER, new McpSchema.TextContent("Test message"))),
-				null, // modelPreferences
-				"Test system prompt", McpSchema.CreateMessageRequest.ContextInclusionStrategy.NONE, 0.7, // temperature
-				100, // maxTokens
-				null, // stopSequences
-				null // metadata
-		);
+		var messageRequest = McpSchema.CreateMessageRequest
+			.builder(List.of(McpSchema.SamplingMessage
+				.builder(McpSchema.Role.USER, McpSchema.TextContent.builder("Test message").build())
+				.build()), 100)
+			.systemPrompt("Test system prompt")
+			.includeContext(McpSchema.CreateMessageRequest.ContextInclusionStrategy.NONE)
+			.temperature(0.7)
+			.build();
 
 		// Simulate incoming request
-		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION,
-				McpSchema.METHOD_SAMPLING_CREATE_MESSAGE, "test-id", messageRequest);
+		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(McpSchema.METHOD_SAMPLING_CREATE_MESSAGE,
+				"test-id", messageRequest);
 		transport.simulateIncomingMessage(request);
 
 		// Verify response
@@ -354,13 +363,13 @@ class McpAsyncClientResponseHandlerTests {
 		assertThat(asyncMcpClient.initialize().block()).isNotNull();
 
 		// Create a mock create message request
-		var messageRequest = new McpSchema.CreateMessageRequest(
-				List.of(new McpSchema.SamplingMessage(McpSchema.Role.USER, new McpSchema.TextContent("Test message"))),
-				null, null, null, null, 0, null, null);
+		var messageRequest = McpSchema.CreateMessageRequest.builder(List.of(McpSchema.SamplingMessage
+			.builder(McpSchema.Role.USER, McpSchema.TextContent.builder("Test message").build())
+			.build()), 0).build();
 
 		// Simulate incoming request
-		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION,
-				McpSchema.METHOD_SAMPLING_CREATE_MESSAGE, "test-id", messageRequest);
+		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(McpSchema.METHOD_SAMPLING_CREATE_MESSAGE,
+				"test-id", messageRequest);
 		transport.simulateIncomingMessage(request);
 
 		// Verify error response
@@ -402,8 +411,7 @@ class McpAsyncClientResponseHandlerTests {
 			assertThat(properties).isNotNull();
 			assertThat(((Map<String, Object>) properties).get("message")).isInstanceOf(Map.class);
 
-			return Mono.just(McpSchema.ElicitResult.builder()
-				.message(McpSchema.ElicitResult.Action.ACCEPT)
+			return Mono.just(McpSchema.ElicitResult.builder(McpSchema.ElicitResult.Action.ACCEPT)
 				.content(Map.of("message", request.message()))
 				.build());
 		};
@@ -417,14 +425,14 @@ class McpAsyncClientResponseHandlerTests {
 		assertThat(asyncMcpClient.initialize().block()).isNotNull();
 
 		// Create a mock elicitation
-		var elicitRequest = McpSchema.ElicitRequest.builder()
-			.message("Test message")
-			.requestedSchema(Map.of("type", "object", "properties", Map.of("message", Map.of("type", "string"))))
+		var elicitRequest = McpSchema.ElicitRequest
+			.builder("Test message",
+					Map.of("type", "object", "properties", Map.of("message", Map.of("type", "string"))))
 			.build();
 
 		// Simulate incoming request
-		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION,
-				McpSchema.METHOD_ELICITATION_CREATE, "test-id", elicitRequest);
+		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(McpSchema.METHOD_ELICITATION_CREATE, "test-id",
+				elicitRequest);
 		transport.simulateIncomingMessage(request);
 
 		// Verify response
@@ -451,7 +459,7 @@ class McpAsyncClientResponseHandlerTests {
 
 		// Create a test elicitation handler to decline the request
 		Function<McpSchema.ElicitRequest, Mono<McpSchema.ElicitResult>> elicitationHandler = request -> Mono
-			.just(McpSchema.ElicitResult.builder().message(action).build());
+			.just(McpSchema.ElicitResult.builder(action).build());
 
 		// Create client with elicitation capability and handler
 		McpAsyncClient asyncMcpClient = McpClient.async(transport)
@@ -462,14 +470,14 @@ class McpAsyncClientResponseHandlerTests {
 		assertThat(asyncMcpClient.initialize().block()).isNotNull();
 
 		// Create a mock elicitation
-		var elicitRequest = McpSchema.ElicitRequest.builder()
-			.message("Test message")
-			.requestedSchema(Map.of("type", "object", "properties", Map.of("message", Map.of("type", "string"))))
+		var elicitRequest = McpSchema.ElicitRequest
+			.builder("Test message",
+					Map.of("type", "object", "properties", Map.of("message", Map.of("type", "string"))))
 			.build();
 
 		// Simulate incoming request
-		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION,
-				McpSchema.METHOD_ELICITATION_CREATE, "test-id", elicitRequest);
+		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(McpSchema.METHOD_ELICITATION_CREATE, "test-id",
+				elicitRequest);
 		transport.simulateIncomingMessage(request);
 
 		// Verify response
@@ -502,13 +510,15 @@ class McpAsyncClientResponseHandlerTests {
 		assertThat(asyncMcpClient.initialize().block()).isNotNull();
 
 		// Create a mock elicitation
-		var elicitRequest = new McpSchema.ElicitRequest("test",
-				Map.of("type", "object", "properties", Map.of("test", Map.of("type", "boolean", "defaultValue", true,
-						"description", "test-description", "title", "test-title"))));
+		var elicitRequest = McpSchema.ElicitRequest
+			.builder("test",
+					Map.of("type", "object", "properties", Map.of("test", Map.of("type", "boolean", "defaultValue",
+							true, "description", "test-description", "title", "test-title"))))
+			.build();
 
 		// Simulate incoming request
-		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION,
-				McpSchema.METHOD_ELICITATION_CREATE, "test-id", elicitRequest);
+		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(McpSchema.METHOD_ELICITATION_CREATE, "test-id",
+				elicitRequest);
 		transport.simulateIncomingMessage(request);
 
 		// Verify error response
@@ -544,8 +554,7 @@ class McpAsyncClientResponseHandlerTests {
 		assertThat(asyncMcpClient.initialize().block()).isNotNull();
 
 		// Simulate incoming ping request from server
-		McpSchema.JSONRPCRequest pingRequest = new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION,
-				McpSchema.METHOD_PING, "ping-id", null);
+		McpSchema.JSONRPCRequest pingRequest = new McpSchema.JSONRPCRequest(McpSchema.METHOD_PING, "ping-id");
 		transport.simulateIncomingMessage(pingRequest);
 
 		// Verify response

mcp-test/src/test/java/io/modelcontextprotocol/client/McpAsyncClientTests.java

@@ -26,15 +26,18 @@ import static org.assertj.core.api.Assertions.assertThatCode;
 
 class McpAsyncClientTests {
 
-	public static final McpSchema.Implementation MOCK_SERVER_INFO = new McpSchema.Implementation("test-server",
-			"1.0.0");
+	public static final McpSchema.Implementation MOCK_SERVER_INFO = McpSchema.Implementation
+		.builder("test-server", "1.0.0")
+		.build();
 
 	public static final McpSchema.ServerCapabilities MOCK_SERVER_CAPABILITIES = McpSchema.ServerCapabilities.builder()
 		.tools(true)
 		.build();
 
-	public static final McpSchema.InitializeResult MOCK_INIT_RESULT = new McpSchema.InitializeResult(
-			ProtocolVersions.MCP_2024_11_05, MOCK_SERVER_CAPABILITIES, MOCK_SERVER_INFO, "Test instructions");
+	public static final McpSchema.InitializeResult MOCK_INIT_RESULT = McpSchema.InitializeResult
+		.builder(ProtocolVersions.MCP_2024_11_05, MOCK_SERVER_CAPABILITIES, MOCK_SERVER_INFO)
+		.instructions("Test instructions")
+		.build();
 
 	private static final String CONTEXT_KEY = "context.key";
 
@@ -44,10 +47,8 @@ class McpAsyncClientTests {
 		Map<String, Object> inputSchemaMap = Map.of("type", "object", "properties",
 				Map.of("expression", Map.of("type", "string")), "required", List.of("expression"));
 
-		McpSchema.Tool.Builder toolBuilder = McpSchema.Tool.builder()
-			.name("calculator")
-			.description("Performs mathematical calculations")
-			.inputSchema(inputSchemaMap);
+		McpSchema.Tool.Builder toolBuilder = McpSchema.Tool.builder("calculator", inputSchemaMap)
+			.description("Performs mathematical calculations");
 
 		if (hasOutputSchema) {
 			Map<String, Object> outputSchema = Map.of("type", "object", "properties",
@@ -57,7 +58,7 @@ class McpAsyncClientTests {
 		}
 
 		McpSchema.Tool calculatorTool = toolBuilder.build();
-		McpSchema.ListToolsResult mockToolsResult = new McpSchema.ListToolsResult(List.of(calculatorTool), null);
+		McpSchema.ListToolsResult mockToolsResult = McpSchema.ListToolsResult.builder(List.of(calculatorTool)).build();
 
 		// Create call tool result - valid or invalid based on parameter
 		Map<String, Object> structuredContent = invalidOutput ? Map.of("result", "5", "operation", "add")
@@ -91,16 +92,13 @@ class McpAsyncClientTests {
 
 				McpSchema.JSONRPCResponse response;
 				if (McpSchema.METHOD_INITIALIZE.equals(request.method())) {
-					response = new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION, request.id(), MOCK_INIT_RESULT,
-							null);
+					response = McpSchema.JSONRPCResponse.result(request.id(), MOCK_INIT_RESULT);
 				}
 				else if (McpSchema.METHOD_TOOLS_LIST.equals(request.method())) {
-					response = new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION, request.id(), mockToolsResult,
-							null);
+					response = McpSchema.JSONRPCResponse.result(request.id(), mockToolsResult);
 				}
 				else if (McpSchema.METHOD_TOOLS_CALL.equals(request.method())) {
-					response = new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION, request.id(),
-							mockCallToolResult, null);
+					response = McpSchema.JSONRPCResponse.result(request.id(), mockCallToolResult);
 				}
 				else {
 					return Mono.empty();
@@ -155,8 +153,8 @@ class McpAsyncClientTests {
 				if (!(message instanceof McpSchema.JSONRPCRequest)) {
 					return Mono.empty();
 				}
-				McpSchema.JSONRPCResponse initResponse = new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION,
-						((McpSchema.JSONRPCRequest) message).id(), MOCK_INIT_RESULT, null);
+				McpSchema.JSONRPCResponse initResponse = McpSchema.JSONRPCResponse
+					.result(((McpSchema.JSONRPCRequest) message).id(), MOCK_INIT_RESULT);
 				return handler.apply(Mono.just(initResponse)).then();
 			}
 
@@ -185,7 +183,9 @@ class McpAsyncClientTests {
 
 		StepVerifier.create(client.initialize()).expectNextMatches(Objects::nonNull).verifyComplete();
 
-		StepVerifier.create(client.callTool(new McpSchema.CallToolRequest("calculator", Map.of("expression", "2 + 3"))))
+		StepVerifier
+			.create(client.callTool(
+					McpSchema.CallToolRequest.builder("calculator").arguments(Map.of("expression", "2 + 3")).build()))
 			.expectNextMatches(response -> {
 				assertThat(response).isNotNull();
 				assertThat(response.isError()).isFalse();
@@ -207,7 +207,9 @@ class McpAsyncClientTests {
 
 		StepVerifier.create(client.initialize()).expectNextMatches(Objects::nonNull).verifyComplete();
 
-		StepVerifier.create(client.callTool(new McpSchema.CallToolRequest("calculator", Map.of("expression", "2 + 3"))))
+		StepVerifier
+			.create(client.callTool(
+					McpSchema.CallToolRequest.builder("calculator").arguments(Map.of("expression", "2 + 3")).build()))
 			.expectNextMatches(response -> {
 				assertThat(response).isNotNull();
 				assertThat(response.isError()).isFalse();
@@ -229,7 +231,9 @@ class McpAsyncClientTests {
 
 		StepVerifier.create(client.initialize()).expectNextMatches(Objects::nonNull).verifyComplete();
 
-		StepVerifier.create(client.callTool(new McpSchema.CallToolRequest("calculator", Map.of("expression", "2 + 3"))))
+		StepVerifier
+			.create(client.callTool(
+					McpSchema.CallToolRequest.builder("calculator").arguments(Map.of("expression", "2 + 3")).build()))
 			.expectErrorMatches(ex -> ex instanceof IllegalArgumentException
 					&& ex.getMessage().contains("Tool call result validation failed"))
 			.verify();
@@ -326,50 +330,50 @@ class McpAsyncClientTests {
 					.tools(false)
 					.build();
 
-				McpSchema.InitializeResult initResult = new McpSchema.InitializeResult(ProtocolVersions.MCP_2024_11_05,
-						caps, MOCK_SERVER_INFO, null);
+				McpSchema.InitializeResult initResult = McpSchema.InitializeResult
+					.builder(ProtocolVersions.MCP_2024_11_05, caps, MOCK_SERVER_INFO)
+					.build();
 
-				response = new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION, request.id(), initResult, null);
+				response = McpSchema.JSONRPCResponse.result(request.id(), initResult);
 			}
 			else if (McpSchema.METHOD_PROMPT_LIST.equals(request.method())) {
 				capturedRequest = JSON_MAPPER.convertValue(request.params(), McpSchema.PaginatedRequest.class);
 
-				McpSchema.Prompt mockPrompt = new McpSchema.Prompt("test-prompt", "A test prompt", List.of());
-				McpSchema.ListPromptsResult mockPromptResult = new McpSchema.ListPromptsResult(List.of(mockPrompt),
-						null);
-				response = new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION, request.id(), mockPromptResult,
-						null);
+				McpSchema.Prompt mockPrompt = McpSchema.Prompt.builder("test-prompt")
+					.description("A test prompt")
+					.arguments(List.of())
+					.build();
+				McpSchema.ListPromptsResult mockPromptResult = McpSchema.ListPromptsResult.builder(List.of(mockPrompt))
+					.build();
+				response = McpSchema.JSONRPCResponse.result(request.id(), mockPromptResult);
 			}
 			else if (McpSchema.METHOD_RESOURCES_TEMPLATES_LIST.equals(request.method())) {
 				capturedRequest = JSON_MAPPER.convertValue(request.params(), McpSchema.PaginatedRequest.class);
 
-				McpSchema.ResourceTemplate mockTemplate = new McpSchema.ResourceTemplate("file:///{name}", "template",
-						null, null, null);
-				McpSchema.ListResourceTemplatesResult mockResourceTemplateResult = new McpSchema.ListResourceTemplatesResult(
-						List.of(mockTemplate), null);
-				response = new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION, request.id(),
-						mockResourceTemplateResult, null);
+				McpSchema.ResourceTemplate mockTemplate = McpSchema.ResourceTemplate
+					.builder("file:///{name}", "template")
+					.build();
+				McpSchema.ListResourceTemplatesResult mockResourceTemplateResult = McpSchema.ListResourceTemplatesResult
+					.builder(List.of(mockTemplate))
+					.build();
+				response = McpSchema.JSONRPCResponse.result(request.id(), mockResourceTemplateResult);
 			}
 			else if (McpSchema.METHOD_RESOURCES_LIST.equals(request.method())) {
 				capturedRequest = JSON_MAPPER.convertValue(request.params(), McpSchema.PaginatedRequest.class);
 
-				McpSchema.Resource mockResource = McpSchema.Resource.builder()
-					.uri("file:///test.txt")
-					.name("test.txt")
+				McpSchema.Resource mockResource = McpSchema.Resource.builder("file:///test.txt", "test.txt").build();
+				McpSchema.ListResourcesResult mockResourceResult = McpSchema.ListResourcesResult
+					.builder(List.of(mockResource))
 					.build();
-				McpSchema.ListResourcesResult mockResourceResult = new McpSchema.ListResourcesResult(
-						List.of(mockResource), null);
 
-				response = new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION, request.id(), mockResourceResult,
-						null);
+				response = McpSchema.JSONRPCResponse.result(request.id(), mockResourceResult);
 			}
 			else if (McpSchema.METHOD_TOOLS_LIST.equals(request.method())) {
 				capturedRequest = JSON_MAPPER.convertValue(request.params(), McpSchema.PaginatedRequest.class);
 
-				McpSchema.Tool addTool = McpSchema.Tool.builder().name("add").description("calculate add").build();
-				McpSchema.ListToolsResult mockToolsResult = new McpSchema.ListToolsResult(List.of(addTool), null);
-				response = new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION, request.id(), mockToolsResult,
-						null);
+				McpSchema.Tool addTool = McpSchema.Tool.builder("add").description("calculate add").build();
+				McpSchema.ListToolsResult mockToolsResult = McpSchema.ListToolsResult.builder(List.of(addTool)).build();
+				response = McpSchema.JSONRPCResponse.result(request.id(), mockToolsResult);
 			}
 			else {
 				return Mono.empty();

mcp-test/src/test/java/io/modelcontextprotocol/client/McpClientProtocolVersionTests.java

@@ -25,7 +25,8 @@ class McpClientProtocolVersionTests {
 
 	private static final Duration REQUEST_TIMEOUT = Duration.ofSeconds(300);
 
-	private static final McpSchema.Implementation CLIENT_INFO = new McpSchema.Implementation("test-client", "1.0.0");
+	private static final McpSchema.Implementation CLIENT_INFO = McpSchema.Implementation.builder("test-client", "1.0.0")
+		.build();
 
 	@Test
 	void shouldUseLatestVersionByDefault() {
@@ -46,10 +47,11 @@ class McpClientProtocolVersionTests {
 				McpSchema.InitializeRequest initRequest = (McpSchema.InitializeRequest) request.params();
 				assertThat(initRequest.protocolVersion()).isEqualTo(transport.protocolVersions().get(0));
 
-				transport.simulateIncomingMessage(new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION, request.id(),
-						new McpSchema.InitializeResult(protocolVersion, ServerCapabilities.builder().build(),
-								new McpSchema.Implementation("test-server", "1.0.0"), null),
-						null));
+				transport.simulateIncomingMessage(McpSchema.JSONRPCResponse.result(request.id(),
+						McpSchema.InitializeResult
+							.builder(protocolVersion, ServerCapabilities.builder().build(),
+									McpSchema.Implementation.builder("test-server", "1.0.0").build())
+							.build()));
 			}).assertNext(result -> {
 				assertThat(result.protocolVersion()).isEqualTo(protocolVersion);
 			}).verifyComplete();
@@ -80,10 +82,11 @@ class McpClientProtocolVersionTests {
 				McpSchema.InitializeRequest initRequest = (McpSchema.InitializeRequest) request.params();
 				assertThat(initRequest.protocolVersion()).isIn(List.of(oldVersion, ProtocolVersions.MCP_2025_11_25));
 
-				transport.simulateIncomingMessage(new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION, request.id(),
-						new McpSchema.InitializeResult(oldVersion, ServerCapabilities.builder().build(),
-								new McpSchema.Implementation("test-server", "1.0.0"), null),
-						null));
+				transport.simulateIncomingMessage(McpSchema.JSONRPCResponse.result(request.id(),
+						McpSchema.InitializeResult
+							.builder(oldVersion, ServerCapabilities.builder().build(),
+									McpSchema.Implementation.builder("test-server", "1.0.0").build())
+							.build()));
 			}).assertNext(result -> {
 				assertThat(result.protocolVersion()).isEqualTo(oldVersion);
 			}).verifyComplete();
@@ -109,10 +112,11 @@ class McpClientProtocolVersionTests {
 				McpSchema.JSONRPCRequest request = transport.getLastSentMessageAsRequest();
 				assertThat(request.params()).isInstanceOf(McpSchema.InitializeRequest.class);
 
-				transport.simulateIncomingMessage(new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION, request.id(),
-						new McpSchema.InitializeResult(unsupportedVersion, ServerCapabilities.builder().build(),
-								new McpSchema.Implementation("test-server", "1.0.0"), null),
-						null));
+				transport.simulateIncomingMessage(McpSchema.JSONRPCResponse.result(request.id(),
+						McpSchema.InitializeResult
+							.builder(unsupportedVersion, ServerCapabilities.builder().build(),
+									McpSchema.Implementation.builder("test-server", "1.0.0").build())
+							.build()));
 			}).expectError(RuntimeException.class).verify();
 		}
 		finally {
@@ -142,10 +146,11 @@ class McpClientProtocolVersionTests {
 				McpSchema.InitializeRequest initRequest = (McpSchema.InitializeRequest) request.params();
 				assertThat(initRequest.protocolVersion()).isEqualTo(latestVersion);
 
-				transport.simulateIncomingMessage(new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION, request.id(),
-						new McpSchema.InitializeResult(latestVersion, ServerCapabilities.builder().build(),
-								new McpSchema.Implementation("test-server", "1.0.0"), null),
-						null));
+				transport.simulateIncomingMessage(McpSchema.JSONRPCResponse.result(request.id(),
+						McpSchema.InitializeResult
+							.builder(latestVersion, ServerCapabilities.builder().build(),
+									McpSchema.Implementation.builder("test-server", "1.0.0").build())
+							.build()));
 			}).assertNext(result -> {
 				assertThat(result.protocolVersion()).isEqualTo(latestVersion);
 			}).verifyComplete();

mcp-test/src/test/java/io/modelcontextprotocol/client/transport/HttpClientSseClientTransportTests.java

@@ -13,6 +13,8 @@ import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.Function;
 
+import com.fasterxml.jackson.annotation.JsonIgnore;
+import com.fasterxml.jackson.annotation.JsonProperty;
 import io.modelcontextprotocol.client.transport.customizer.McpAsyncHttpClientRequestCustomizer;
 import io.modelcontextprotocol.client.transport.customizer.McpSyncHttpClientRequestCustomizer;
 import io.modelcontextprotocol.common.McpTransportContext;
@@ -126,8 +128,7 @@ class HttpClientSseClientTransportTests {
 
 	@Test
 	void testErrorOnBogusMessage() {
-		// bogus message
-		JSONRPCRequest bogusMessage = new JSONRPCRequest(null, null, "test-id", Map.of("key", "value"));
+		var bogusMessage = new BogusJsonRpcMessage("test-id", Map.of("key", "value"));
 
 		StepVerifier.create(transport.sendMessage(bogusMessage))
 			.verifyErrorMessage(
@@ -137,8 +138,7 @@ class HttpClientSseClientTransportTests {
 	@Test
 	void testMessageProcessing() {
 		// Create a test message
-		JSONRPCRequest testMessage = new JSONRPCRequest(McpSchema.JSONRPC_VERSION, "test-method", "test-id",
-				Map.of("key", "value"));
+		JSONRPCRequest testMessage = new McpSchema.JSONRPCRequest("test-method", "test-id", Map.of("key", "value"));
 
 		// Simulate receiving the message
 		transport.simulateMessageEvent("""
@@ -168,8 +168,7 @@ class HttpClientSseClientTransportTests {
 				""");
 
 		// Create and send a request message
-		JSONRPCRequest testMessage = new JSONRPCRequest(McpSchema.JSONRPC_VERSION, "test-method", "test-id",
-				Map.of("key", "value"));
+		JSONRPCRequest testMessage = new McpSchema.JSONRPCRequest("test-method", "test-id", Map.of("key", "value"));
 
 		// Verify message handling
 		StepVerifier.create(transport.sendMessage(testMessage)).verifyComplete();
@@ -192,8 +191,7 @@ class HttpClientSseClientTransportTests {
 				""");
 
 		// Create and send a request message
-		JSONRPCRequest testMessage = new JSONRPCRequest(McpSchema.JSONRPC_VERSION, "test-method", "test-id",
-				Map.of("key", "value"));
+		JSONRPCRequest testMessage = new McpSchema.JSONRPCRequest("test-method", "test-id", Map.of("key", "value"));
 
 		// Verify message handling
 		StepVerifier.create(transport.sendMessage(testMessage)).verifyComplete();
@@ -222,8 +220,7 @@ class HttpClientSseClientTransportTests {
 		StepVerifier.create(transport.closeGracefully()).verifyComplete();
 
 		// Create a test message
-		JSONRPCRequest testMessage = new JSONRPCRequest(McpSchema.JSONRPC_VERSION, "test-method", "test-id",
-				Map.of("key", "value"));
+		JSONRPCRequest testMessage = new McpSchema.JSONRPCRequest("test-method", "test-id", Map.of("key", "value"));
 
 		// Verify message is not processed after shutdown
 		StepVerifier.create(transport.sendMessage(testMessage)).verifyComplete();
@@ -267,11 +264,9 @@ class HttpClientSseClientTransportTests {
 				""");
 
 		// Create and send corresponding messages
-		JSONRPCRequest message1 = new JSONRPCRequest(McpSchema.JSONRPC_VERSION, "method1", "id1",
-				Map.of("key", "value1"));
+		JSONRPCRequest message1 = new McpSchema.JSONRPCRequest("method1", "id1", Map.of("key", "value1"));
 
-		JSONRPCRequest message2 = new JSONRPCRequest(McpSchema.JSONRPC_VERSION, "method2", "id2",
-				Map.of("key", "value2"));
+		JSONRPCRequest message2 = new McpSchema.JSONRPCRequest("method2", "id2", Map.of("key", "value2"));
 
 		// Verify both messages are processed
 		StepVerifier.create(transport.sendMessage(message1).then(transport.sendMessage(message2))).verifyComplete();
@@ -355,8 +350,7 @@ class HttpClientSseClientTransportTests {
 		clearInvocations(mockCustomizer);
 
 		// Send test message
-		var testMessage = new JSONRPCRequest(McpSchema.JSONRPC_VERSION, "test-method", "test-id",
-				Map.of("key", "value"));
+		var testMessage = new McpSchema.JSONRPCRequest("test-method", "test-id", Map.of("key", "value"));
 
 		// Subscribe to messages and verify
 		StepVerifier
@@ -398,8 +392,7 @@ class HttpClientSseClientTransportTests {
 		clearInvocations(mockCustomizer);
 
 		// Send test message
-		var testMessage = new JSONRPCRequest(McpSchema.JSONRPC_VERSION, "test-method", "test-id",
-				Map.of("key", "value"));
+		var testMessage = new McpSchema.JSONRPCRequest("test-method", "test-id", Map.of("key", "value"));
 
 		// Subscribe to messages and verify
 		StepVerifier
@@ -458,4 +451,30 @@ class HttpClientSseClientTransportTests {
 		return false;
 	}
 
+	/**
+	 * A minimal {@link McpSchema.JSONRPCMessage} that serializes only the supplied
+	 * fields, intentionally omitting {@code jsonrpc} and {@code method} to produce a
+	 * bogus wire payload for error-handling tests.
+	 */
+	private static class BogusJsonRpcMessage implements McpSchema.JSONRPCMessage {
+
+		@JsonProperty("id")
+		private final String id;
+
+		@JsonProperty("params")
+		private final Map<String, Object> params;
+
+		BogusJsonRpcMessage(String id, Map<String, Object> params) {
+			this.id = id;
+			this.params = params;
+		}
+
+		@Override
+		@JsonIgnore
+		public String jsonrpc() {
+			return null;
+		}
+
+	}
+
 }

mcp-test/src/test/java/io/modelcontextprotocol/client/transport/HttpClientStreamableHttpTransportEmptyJsonResponseTest.java

@@ -76,11 +76,11 @@ public class HttpClientStreamableHttpTransportEmptyJsonResponseTest {
 			.httpRequestCustomizer(mockRequestCustomizer)
 			.build();
 
-		var initializeRequest = new McpSchema.InitializeRequest(ProtocolVersions.MCP_2025_03_26,
-				McpSchema.ClientCapabilities.builder().roots(true).build(),
-				new McpSchema.Implementation("MCP Client", "0.3.1"));
-		var testMessage = new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION, McpSchema.METHOD_INITIALIZE,
-				"test-id", initializeRequest);
+		var initializeRequest = McpSchema.InitializeRequest
+			.builder(ProtocolVersions.MCP_2025_03_26, McpSchema.ClientCapabilities.builder().roots(true).build(),
+					McpSchema.Implementation.builder("MCP Client", "0.3.1").build())
+			.build();
+		var testMessage = new McpSchema.JSONRPCRequest(McpSchema.METHOD_INITIALIZE, "test-id", initializeRequest);
 
 		StepVerifier.create(transport.sendMessage(testMessage)).verifyComplete();
 

mcp-test/src/test/java/io/modelcontextprotocol/client/transport/HttpClientStreamableHttpTransportErrorHandlingTest.java

@@ -770,11 +770,11 @@ public class HttpClientStreamableHttpTransportErrorHandlingTest {
 	}
 
 	private McpSchema.JSONRPCRequest createTestRequestMessage() {
-		var initializeRequest = new McpSchema.InitializeRequest(ProtocolVersions.MCP_2025_03_26,
-				McpSchema.ClientCapabilities.builder().roots(true).build(),
-				new McpSchema.Implementation("Test Client", "1.0.0"));
-		return new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION, McpSchema.METHOD_INITIALIZE, "test-id",
-				initializeRequest);
+		var initializeRequest = McpSchema.InitializeRequest
+			.builder(ProtocolVersions.MCP_2025_03_26, McpSchema.ClientCapabilities.builder().roots(true).build(),
+					McpSchema.Implementation.builder("Test Client", "1.0.0").build())
+			.build();
+		return new McpSchema.JSONRPCRequest(McpSchema.METHOD_INITIALIZE, "test-id", initializeRequest);
 	}
 
 }

mcp-test/src/test/java/io/modelcontextprotocol/client/transport/HttpClientStreamableHttpTransportTest.java

@@ -79,11 +79,11 @@ class HttpClientStreamableHttpTransportTest {
 
 		withTransport(transport, (t) -> {
 			// Send test message
-			var initializeRequest = new McpSchema.InitializeRequest(ProtocolVersions.MCP_2025_11_25,
-					McpSchema.ClientCapabilities.builder().roots(true).build(),
-					new McpSchema.Implementation("MCP Client", "0.3.1"));
-			var testMessage = new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION, McpSchema.METHOD_INITIALIZE,
-					"test-id", initializeRequest);
+			var initializeRequest = McpSchema.InitializeRequest
+				.builder(ProtocolVersions.MCP_2025_11_25, McpSchema.ClientCapabilities.builder().roots(true).build(),
+						McpSchema.Implementation.builder("MCP Client", "0.3.1").build())
+				.build();
+			var testMessage = new McpSchema.JSONRPCRequest(McpSchema.METHOD_INITIALIZE, "test-id", initializeRequest);
 
 			StepVerifier
 				.create(t.sendMessage(testMessage).contextWrite(ctx -> ctx.put(McpTransportContext.KEY, context)))
@@ -109,11 +109,11 @@ class HttpClientStreamableHttpTransportTest {
 
 		withTransport(transport, (t) -> {
 			// Send test message
-			var initializeRequest = new McpSchema.InitializeRequest(ProtocolVersions.MCP_2025_11_25,
-					McpSchema.ClientCapabilities.builder().roots(true).build(),
-					new McpSchema.Implementation("MCP Client", "0.3.1"));
-			var testMessage = new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION, McpSchema.METHOD_INITIALIZE,
-					"test-id", initializeRequest);
+			var initializeRequest = McpSchema.InitializeRequest
+				.builder(ProtocolVersions.MCP_2025_11_25, McpSchema.ClientCapabilities.builder().roots(true).build(),
+						McpSchema.Implementation.builder("MCP Client", "0.3.1").build())
+				.build();
+			var testMessage = new McpSchema.JSONRPCRequest(McpSchema.METHOD_INITIALIZE, "test-id", initializeRequest);
 
 			StepVerifier
 				.create(t.sendMessage(testMessage).contextWrite(ctx -> ctx.put(McpTransportContext.KEY, context)))
@@ -132,11 +132,11 @@ class HttpClientStreamableHttpTransportTest {
 
 		StepVerifier.create(transport.closeGracefully()).verifyComplete();
 
-		var initializeRequest = new McpSchema.InitializeRequest(ProtocolVersions.MCP_2025_11_25,
-				McpSchema.ClientCapabilities.builder().roots(true).build(),
-				new McpSchema.Implementation("MCP Client", "0.3.1"));
-		var testMessage = new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION, McpSchema.METHOD_INITIALIZE,
-				"test-id", initializeRequest);
+		var initializeRequest = McpSchema.InitializeRequest
+			.builder(ProtocolVersions.MCP_2025_11_25, McpSchema.ClientCapabilities.builder().roots(true).build(),
+					McpSchema.Implementation.builder("MCP Client", "0.3.1").build())
+			.build();
+		var testMessage = new McpSchema.JSONRPCRequest(McpSchema.METHOD_INITIALIZE, "test-id", initializeRequest);
 
 		StepVerifier.create(transport.sendMessage(testMessage))
 			.expectErrorMessage("MCP session has been closed")
@@ -147,11 +147,11 @@ class HttpClientStreamableHttpTransportTest {
 	void testCloseInitialized() {
 		var transport = HttpClientStreamableHttpTransport.builder(host).build();
 
-		var initializeRequest = new McpSchema.InitializeRequest(ProtocolVersions.MCP_2025_11_25,
-				McpSchema.ClientCapabilities.builder().roots(true).build(),
-				new McpSchema.Implementation("MCP Client", "0.3.1"));
-		var testMessage = new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION, McpSchema.METHOD_INITIALIZE,
-				"test-id", initializeRequest);
+		var initializeRequest = McpSchema.InitializeRequest
+			.builder(ProtocolVersions.MCP_2025_11_25, McpSchema.ClientCapabilities.builder().roots(true).build(),
+					McpSchema.Implementation.builder("MCP Client", "0.3.1").build())
+			.build();
+		var testMessage = new McpSchema.JSONRPCRequest(McpSchema.METHOD_INITIALIZE, "test-id", initializeRequest);
 
 		StepVerifier.create(transport.sendMessage(testMessage)).verifyComplete();
 		StepVerifier.create(transport.closeGracefully()).verifyComplete();

mcp-test/src/test/java/io/modelcontextprotocol/common/AsyncServerMcpTransportContextIntegrationTests.java

@@ -125,8 +125,7 @@ public class AsyncServerMcpTransportContextIntegrationTests {
 			.build())
 		.build();
 
-	private final McpSchema.Tool tool = McpSchema.Tool.builder()
-		.name("test-tool")
+	private final McpSchema.Tool tool = McpSchema.Tool.builder("test-tool")
 		.description("return the value of the x-test header from call tool request")
 		.build();
 
@@ -178,7 +177,8 @@ public class AsyncServerMcpTransportContextIntegrationTests {
 
 		// Test tool call with context
 		StepVerifier
-			.create(asyncStreamableClient.callTool(new McpSchema.CallToolRequest("test-tool", Map.of()))
+			.create(asyncStreamableClient
+				.callTool(McpSchema.CallToolRequest.builder("test-tool").arguments(Map.of()).build())
 				.contextWrite(ctx -> ctx.put(McpTransportContext.KEY,
 						McpTransportContext.create(Map.of("client-side-header-value", "some important value")))))
 			.assertNext(response -> {
@@ -212,7 +212,8 @@ public class AsyncServerMcpTransportContextIntegrationTests {
 
 		// Test tool call with context
 		StepVerifier
-			.create(asyncStreamableClient.callTool(new McpSchema.CallToolRequest("test-tool", Map.of()))
+			.create(asyncStreamableClient
+				.callTool(McpSchema.CallToolRequest.builder("test-tool").arguments(Map.of()).build())
 				.contextWrite(ctx -> ctx.put(McpTransportContext.KEY,
 						McpTransportContext.create(Map.of("client-side-header-value", "some important value")))))
 			.assertNext(response -> {
@@ -246,7 +247,7 @@ public class AsyncServerMcpTransportContextIntegrationTests {
 
 		// Test tool call with context
 		StepVerifier
-			.create(asyncSseClient.callTool(new McpSchema.CallToolRequest("test-tool", Map.of()))
+			.create(asyncSseClient.callTool(McpSchema.CallToolRequest.builder("test-tool").arguments(Map.of()).build())
 				.contextWrite(ctx -> ctx.put(McpTransportContext.KEY,
 						McpTransportContext.create(Map.of("client-side-header-value", "some important value")))))
 			.assertNext(response -> {

mcp-test/src/test/java/io/modelcontextprotocol/common/HttpClientStreamableHttpVersionNegotiationIntegrationTests.java

@@ -41,8 +41,7 @@ class HttpClientStreamableHttpVersionNegotiationIntegrationTests {
 				req -> McpTransportContext.create(Map.of("protocol-version", req.getHeader("MCP-protocol-version"))))
 		.build();
 
-	private final McpSchema.Tool toolSpec = McpSchema.Tool.builder()
-		.name("test-tool")
+	private final McpSchema.Tool toolSpec = McpSchema.Tool.builder("test-tool")
 		.description("return the protocol version used")
 		.build();
 
@@ -70,7 +69,8 @@ class HttpClientStreamableHttpVersionNegotiationIntegrationTests {
 			.build();
 
 		client.initialize();
-		McpSchema.CallToolResult response = client.callTool(new McpSchema.CallToolRequest("test-tool", Map.of()));
+		McpSchema.CallToolResult response = client
+			.callTool(McpSchema.CallToolRequest.builder("test-tool").arguments(Map.of()).build());
 
 		var calls = requestRecordingFilter.getCalls();
 
@@ -100,7 +100,8 @@ class HttpClientStreamableHttpVersionNegotiationIntegrationTests {
 		var client = McpClient.sync(transport).build();
 
 		client.initialize();
-		McpSchema.CallToolResult response = client.callTool(new McpSchema.CallToolRequest("test-tool", Map.of()));
+		McpSchema.CallToolResult response = client
+			.callTool(McpSchema.CallToolRequest.builder("test-tool").arguments(Map.of()).build());
 
 		var calls = requestRecordingFilter.getCalls();
 		// Initialize tells the server the Client's latest supported version

mcp-test/src/test/java/io/modelcontextprotocol/common/SyncServerMcpTransportContextIntegrationTests.java

@@ -116,8 +116,7 @@ public class SyncServerMcpTransportContextIntegrationTests {
 		.transportContextProvider(clientContextProvider)
 		.build();
 
-	private final McpSchema.Tool tool = McpSchema.Tool.builder()
-		.name("test-tool")
+	private final McpSchema.Tool tool = McpSchema.Tool.builder("test-tool")
 		.description("return the value of the x-test header from call tool request")
 		.build();
 
@@ -156,7 +155,7 @@ public class SyncServerMcpTransportContextIntegrationTests {
 
 		CLIENT_SIDE_HEADER_VALUE_HOLDER.set("some important value");
 		McpSchema.CallToolResult response = streamableClient
-			.callTool(new McpSchema.CallToolRequest("test-tool", Map.of()));
+			.callTool(McpSchema.CallToolRequest.builder("test-tool").arguments(Map.of()).build());
 
 		assertThat(response).isNotNull();
 		assertThat(response.content()).hasSize(1)
@@ -182,7 +181,7 @@ public class SyncServerMcpTransportContextIntegrationTests {
 
 		CLIENT_SIDE_HEADER_VALUE_HOLDER.set("some important value");
 		McpSchema.CallToolResult response = streamableClient
-			.callTool(new McpSchema.CallToolRequest("test-tool", Map.of()));
+			.callTool(McpSchema.CallToolRequest.builder("test-tool").arguments(Map.of()).build());
 
 		assertThat(response).isNotNull();
 		assertThat(response.content()).hasSize(1)
@@ -207,7 +206,8 @@ public class SyncServerMcpTransportContextIntegrationTests {
 		assertThat(initResult).isNotNull();
 
 		CLIENT_SIDE_HEADER_VALUE_HOLDER.set("some important value");
-		McpSchema.CallToolResult response = sseClient.callTool(new McpSchema.CallToolRequest("test-tool", Map.of()));
+		McpSchema.CallToolResult response = sseClient
+			.callTool(McpSchema.CallToolRequest.builder("test-tool").arguments(Map.of()).build());
 
 		assertThat(response).isNotNull();
 		assertThat(response.content()).hasSize(1)

mcp-test/src/test/java/io/modelcontextprotocol/server/HttpServletStatelessIntegrationTests.java

@@ -116,11 +116,11 @@ class HttpServletStatelessIntegrationTests {
 		var clientBuilder = clientBuilders.get(clientType);
 
 		var callResponse = CallToolResult.builder()
-			.content(List.of(new McpSchema.TextContent("CALL RESPONSE")))
+			.content(List.of(McpSchema.TextContent.builder("CALL RESPONSE").build()))
 			.isError(false)
 			.build();
 		McpStatelessServerFeatures.SyncToolSpecification tool1 = new McpStatelessServerFeatures.SyncToolSpecification(
-				Tool.builder().name("tool1").title("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build(),
+				Tool.builder("tool1", EMPTY_JSON_SCHEMA).title("tool1 description").build(),
 				(transportContext, request) -> {
 					// perform a blocking call to a remote service
 					String response = RestClient.create()
@@ -144,7 +144,8 @@ class HttpServletStatelessIntegrationTests {
 
 			assertThat(mcpClient.listTools().tools()).contains(tool1.tool());
 
-			CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("tool1", Map.of()));
+			CallToolResult response = mcpClient
+				.callTool(McpSchema.CallToolRequest.builder("tool1").arguments(Map.of()).build());
 
 			assertThat(response).isNotNull();
 			assertThat(response).isEqualTo(callResponse);
@@ -193,12 +194,17 @@ class HttpServletStatelessIntegrationTests {
 
 		var mcpServer = McpServer.sync(mcpStatelessServerTransport)
 			.capabilities(ServerCapabilities.builder().completions().build())
-			.prompts(new McpStatelessServerFeatures.SyncPromptSpecification(
-					new Prompt("code_review", "Code review", "this is code review prompt",
-							List.of(new PromptArgument("language", "Language", "string", false))),
-					(transportContext, getPromptRequest) -> null))
+			.prompts(new McpStatelessServerFeatures.SyncPromptSpecification(Prompt.builder("code_review")
+				.title("Code review")
+				.description("this is code review prompt")
+				.arguments(List.of(PromptArgument.builder("language")
+					.title("Language")
+					.description("string")
+					.required(false)
+					.build()))
+				.build(), (transportContext, getPromptRequest) -> null))
 			.completions(new McpStatelessServerFeatures.SyncCompletionSpecification(
-					new PromptReference(PromptReference.TYPE, "code_review", "Code review"), completionHandler))
+					PromptReference.builder("code_review").title("Code review").build(), completionHandler))
 			.build();
 
 		try (var mcpClient = clientBuilder.build()) {
@@ -206,9 +212,10 @@ class HttpServletStatelessIntegrationTests {
 			InitializeResult initResult = mcpClient.initialize();
 			assertThat(initResult).isNotNull();
 
-			CompleteRequest request = new CompleteRequest(
-					new PromptReference(PromptReference.TYPE, "code_review", "Code review"),
-					new CompleteRequest.CompleteArgument("language", "py"));
+			CompleteRequest request = CompleteRequest
+				.builder(PromptReference.builder("code_review").title("Code review").build(),
+						new CompleteRequest.CompleteArgument("language", "py"))
+				.build();
 
 			CompleteResult result = mcpClient.completeCompletion(request);
 
@@ -237,8 +244,7 @@ class HttpServletStatelessIntegrationTests {
 						Map.of("type", "string"), "timestamp", Map.of("type", "string")),
 				"required", List.of("result", "operation"));
 
-		Tool calculatorTool = Tool.builder()
-			.name("calculator")
+		Tool calculatorTool = Tool.builder("calculator")
 			.description("Performs mathematical calculations")
 			.outputSchema(outputSchema)
 			.build();
@@ -270,8 +276,8 @@ class HttpServletStatelessIntegrationTests {
 			// Note: outputSchema might be null in sync server, but validation still works
 
 			// Call tool with valid structured output
-			CallToolResult response = mcpClient
-				.callTool(new McpSchema.CallToolRequest("calculator", Map.of("expression", "2 + 3")));
+			CallToolResult response = mcpClient.callTool(
+					McpSchema.CallToolRequest.builder("calculator").arguments(Map.of("expression", "2 + 3")).build());
 
 			assertThat(response).isNotNull();
 			assertThat(response.isError()).isFalse();
@@ -312,8 +318,7 @@ class HttpServletStatelessIntegrationTests {
 					"age", Map.of("type", "number")),					
 				"required", List.of("name", "age"))); // @formatter:on
 
-		Tool calculatorTool = Tool.builder()
-			.name("getMembers")
+		Tool calculatorTool = Tool.builder("getMembers")
 			.description("Returns a list of members")
 			.outputSchema(outputSchema)
 			.build();
@@ -338,7 +343,8 @@ class HttpServletStatelessIntegrationTests {
 			assertThat(mcpClient.initialize()).isNotNull();
 
 			// Call tool with valid structured output of type array
-			CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("getMembers", Map.of()));
+			CallToolResult response = mcpClient
+				.callTool(McpSchema.CallToolRequest.builder("getMembers").arguments(Map.of()).build());
 
 			assertThat(response).isNotNull();
 			assertThat(response.isError()).isFalse();
@@ -368,8 +374,7 @@ class HttpServletStatelessIntegrationTests {
 						Map.of("type", "string"), "timestamp", Map.of("type", "string")),
 				"required", List.of("result", "operation"));
 
-		Tool calculatorTool = Tool.builder()
-			.name("calculator")
+		Tool calculatorTool = Tool.builder("calculator")
 			.description("Performs mathematical calculations")
 			.outputSchema(outputSchema)
 			.build();
@@ -380,7 +385,7 @@ class HttpServletStatelessIntegrationTests {
 			.tool(calculatorTool)
 			.callHandler((exchange, request) -> CallToolResult.builder()
 				.isError(true)
-				.content(List.of(new TextContent("Error calling tool: Simulated in-handler error")))
+				.content(List.of(TextContent.builder("Error calling tool: Simulated in-handler error").build()))
 				.build())
 			.build();
 
@@ -401,14 +406,14 @@ class HttpServletStatelessIntegrationTests {
 			// Note: outputSchema might be null in sync server, but validation still works
 
 			// Call tool with valid structured output
-			CallToolResult response = mcpClient
-				.callTool(new McpSchema.CallToolRequest("calculator", Map.of("expression", "2 + 3")));
+			CallToolResult response = mcpClient.callTool(
+					McpSchema.CallToolRequest.builder("calculator").arguments(Map.of("expression", "2 + 3")).build());
 
 			assertThat(response).isNotNull();
 			assertThat(response.isError()).isTrue();
 			assertThat(response.content()).isNotEmpty();
-			assertThat(response.content())
-				.containsExactly(new McpSchema.TextContent("Error calling tool: Simulated in-handler error"));
+			assertThat(response.content()).containsExactly(
+					McpSchema.TextContent.builder("Error calling tool: Simulated in-handler error").build());
 			assertThat(response.structuredContent()).isNull();
 		}
 		finally {
@@ -426,8 +431,7 @@ class HttpServletStatelessIntegrationTests {
 				Map.of("result", Map.of("type", "number"), "operation", Map.of("type", "string")), "required",
 				List.of("result", "operation"));
 
-		Tool calculatorTool = Tool.builder()
-			.name("calculator")
+		Tool calculatorTool = Tool.builder("calculator")
 			.description("Performs mathematical calculations")
 			.outputSchema(outputSchema)
 			.build();
@@ -453,8 +457,8 @@ class HttpServletStatelessIntegrationTests {
 			assertThat(initResult).isNotNull();
 
 			// Call tool with invalid structured output
-			CallToolResult response = mcpClient
-				.callTool(new McpSchema.CallToolRequest("calculator", Map.of("expression", "2 + 3")));
+			CallToolResult response = mcpClient.callTool(
+					McpSchema.CallToolRequest.builder("calculator").arguments(Map.of("expression", "2 + 3")).build());
 
 			assertThat(response).isNotNull();
 			assertThat(response.isError()).isTrue();
@@ -478,8 +482,7 @@ class HttpServletStatelessIntegrationTests {
 		Map<String, Object> outputSchema = Map.of("type", "object", "properties",
 				Map.of("result", Map.of("type", "number")), "required", List.of("result"));
 
-		Tool calculatorTool = Tool.builder()
-			.name("calculator")
+		Tool calculatorTool = Tool.builder("calculator")
 			.description("Performs mathematical calculations")
 			.outputSchema(outputSchema)
 			.build();
@@ -502,8 +505,8 @@ class HttpServletStatelessIntegrationTests {
 			assertThat(initResult).isNotNull();
 
 			// Call tool that should return structured content but doesn't
-			CallToolResult response = mcpClient
-				.callTool(new McpSchema.CallToolRequest("calculator", Map.of("expression", "2 + 3")));
+			CallToolResult response = mcpClient.callTool(
+					McpSchema.CallToolRequest.builder("calculator").arguments(Map.of("expression", "2 + 3")).build());
 
 			assertThat(response).isNotNull();
 			assertThat(response.isError()).isTrue();
@@ -542,8 +545,7 @@ class HttpServletStatelessIntegrationTests {
 					Map.of("message", Map.of("type", "string"), "count", Map.of("type", "integer")), "required",
 					List.of("message", "count"));
 
-			Tool dynamicTool = Tool.builder()
-				.name("dynamic-tool")
+			Tool dynamicTool = Tool.builder("dynamic-tool")
 				.description("Dynamically added tool")
 				.outputSchema(outputSchema)
 				.build();
@@ -573,7 +575,7 @@ class HttpServletStatelessIntegrationTests {
 
 			// Call dynamically added tool
 			CallToolResult response = mcpClient
-				.callTool(new McpSchema.CallToolRequest("dynamic-tool", Map.of("count", 3)));
+				.callTool(McpSchema.CallToolRequest.builder("dynamic-tool").arguments(Map.of("count", 3)).build());
 
 			assertThat(response).isNotNull();
 			assertThat(response.isError()).isFalse();
@@ -601,7 +603,7 @@ class HttpServletStatelessIntegrationTests {
 			.capabilities(ServerCapabilities.builder().tools(true).build())
 			.build();
 
-		Tool testTool = Tool.builder().name("test").description("test").build();
+		Tool testTool = Tool.builder("test").description("test").build();
 
 		McpStatelessServerFeatures.SyncToolSpecification toolSpec = new McpStatelessServerFeatures.SyncToolSpecification(
 				testTool, (transportContext, request) -> {
@@ -610,9 +612,11 @@ class HttpServletStatelessIntegrationTests {
 
 		mcpServer.addTool(toolSpec);
 
-		McpSchema.CallToolRequest callToolRequest = new McpSchema.CallToolRequest("test", Map.of());
-		McpSchema.JSONRPCRequest jsonrpcRequest = new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION,
-				McpSchema.METHOD_TOOLS_CALL, "test", callToolRequest);
+		McpSchema.CallToolRequest callToolRequest = McpSchema.CallToolRequest.builder("test")
+			.arguments(Map.of())
+			.build();
+		McpSchema.JSONRPCRequest jsonrpcRequest = new McpSchema.JSONRPCRequest(McpSchema.METHOD_TOOLS_CALL, "test",
+				callToolRequest);
 
 		MockHttpServletRequest request = new MockHttpServletRequest("POST", CUSTOM_MESSAGE_ENDPOINT);
 		MockHttpServletResponse response = new MockHttpServletResponse();

mcp-test/src/test/java/io/modelcontextprotocol/server/McpCompletionTests.java

@@ -98,11 +98,9 @@ class McpCompletionTests {
 			return new CompleteResult(new CompleteResult.CompleteCompletion(List.of("test-completion"), 1, false));
 		};
 
-		ResourceReference resourceRef = new ResourceReference(ResourceReference.TYPE, "test://resource/{param}");
+		ResourceReference resourceRef = new ResourceReference("test://resource/{param}");
 
-		var resource = Resource.builder()
-			.uri("test://resource/{param}")
-			.name("Test Resource")
+		var resource = Resource.builder("test://resource/{param}", "Test Resource")
 			.description("A resource for testing")
 			.mimeType("text/plain")
 			.size(123L)
@@ -111,19 +109,21 @@ class McpCompletionTests {
 		var mcpServer = McpServer.sync(mcpServerTransportProvider)
 			.capabilities(ServerCapabilities.builder().completions().build())
 			.resources(new McpServerFeatures.SyncResourceSpecification(resource,
-					(exchange, req) -> new ReadResourceResult(List.of())))
+					(exchange, req) -> ReadResourceResult.builder(List.of()).build()))
 			.completions(new McpServerFeatures.SyncCompletionSpecification(resourceRef, completionHandler))
 			.build();
 
-		try (var mcpClient = clientBuilder.clientInfo(new McpSchema.Implementation("Sample " + "client", "0.0.0"))
+		try (var mcpClient = clientBuilder
+			.clientInfo(McpSchema.Implementation.builder("Sample " + "client", "0.0.0").build())
 			.build();) {
 			InitializeResult initResult = mcpClient.initialize();
 			assertThat(initResult).isNotNull();
 
 			// Test with context
-			CompleteRequest request = new CompleteRequest(resourceRef,
-					new CompleteRequest.CompleteArgument("param", "test"), null,
-					new CompleteRequest.CompleteContext(Map.of("previous", "value")));
+			CompleteRequest request = CompleteRequest
+				.builder(resourceRef, new CompleteRequest.CompleteArgument("param", "test"))
+				.context(new CompleteRequest.CompleteContext(Map.of("previous", "value")))
+				.build();
 
 			CompleteResult result = mcpClient.completeCompletion(request);
 
@@ -145,25 +145,29 @@ class McpCompletionTests {
 					new CompleteResult.CompleteCompletion(List.of("no-context-completion"), 1, false));
 		};
 
-		McpSchema.Prompt prompt = new Prompt("test-prompt", "this is a test prompt",
-				List.of(new PromptArgument("arg", "string", false)));
+		McpSchema.Prompt prompt = Prompt.builder("test-prompt")
+			.description("this is a test prompt")
+			.arguments(List.of(PromptArgument.builder("arg").description("string").required(false).build()))
+			.build();
 
 		var mcpServer = McpServer.sync(mcpServerTransportProvider)
 			.capabilities(ServerCapabilities.builder().completions().build())
 			.prompts(new McpServerFeatures.SyncPromptSpecification(prompt,
 					(mcpSyncServerExchange, getPromptRequest) -> null))
-			.completions(new McpServerFeatures.SyncCompletionSpecification(
-					new PromptReference(PromptReference.TYPE, "test-prompt"), completionHandler))
+			.completions(new McpServerFeatures.SyncCompletionSpecification(new PromptReference("test-prompt"),
+					completionHandler))
 			.build();
 
-		try (var mcpClient = clientBuilder.clientInfo(new McpSchema.Implementation("Sample " + "client", "0.0.0"))
+		try (var mcpClient = clientBuilder
+			.clientInfo(McpSchema.Implementation.builder("Sample " + "client", "0.0.0").build())
 			.build();) {
 			InitializeResult initResult = mcpClient.initialize();
 			assertThat(initResult).isNotNull();
 
 			// Test without context
-			CompleteRequest request = new CompleteRequest(new PromptReference(PromptReference.TYPE, "test-prompt"),
-					new CompleteRequest.CompleteArgument("arg", "val"));
+			CompleteRequest request = CompleteRequest
+				.builder(new PromptReference("test-prompt"), new CompleteRequest.CompleteArgument("arg", "val"))
+				.build();
 
 			CompleteResult result = mcpClient.completeCompletion(request);
 
@@ -205,9 +209,7 @@ class McpCompletionTests {
 			return new CompleteResult(new CompleteResult.CompleteCompletion(List.of(), 0, false));
 		};
 
-		McpSchema.Resource resource = Resource.builder()
-			.uri("db://{database}/{table}")
-			.name("Database Table")
+		McpSchema.Resource resource = Resource.builder("db://{database}/{table}", "Database Table")
 			.description("Resource representing a table in a database")
 			.mimeType("application/json")
 			.size(456L)
@@ -216,38 +218,42 @@ class McpCompletionTests {
 		var mcpServer = McpServer.sync(mcpServerTransportProvider)
 			.capabilities(ServerCapabilities.builder().completions().build())
 			.resources(new McpServerFeatures.SyncResourceSpecification(resource,
-					(exchange, req) -> new ReadResourceResult(List.of())))
+					(exchange, req) -> ReadResourceResult.builder(List.of()).build()))
 			.completions(new McpServerFeatures.SyncCompletionSpecification(
-					new ResourceReference(ResourceReference.TYPE, "db://{database}/{table}"), completionHandler))
+					new ResourceReference("db://{database}/{table}"), completionHandler))
 			.build();
 
-		try (var mcpClient = clientBuilder.clientInfo(new McpSchema.Implementation("Sample " + "client", "0.0.0"))
+		try (var mcpClient = clientBuilder
+			.clientInfo(McpSchema.Implementation.builder("Sample " + "client", "0.0.0").build())
 			.build();) {
 			InitializeResult initResult = mcpClient.initialize();
 			assertThat(initResult).isNotNull();
 
 			// First, complete database
-			CompleteRequest dbRequest = new CompleteRequest(
-					new ResourceReference(ResourceReference.TYPE, "db://{database}/{table}"),
-					new CompleteRequest.CompleteArgument("database", ""));
+			CompleteRequest dbRequest = CompleteRequest
+				.builder(new ResourceReference("db://{database}/{table}"),
+						new CompleteRequest.CompleteArgument("database", ""))
+				.build();
 
 			CompleteResult dbResult = mcpClient.completeCompletion(dbRequest);
 			assertThat(dbResult.completion().values()).contains("users_db", "products_db");
 
 			// Then complete table with database context
-			CompleteRequest tableRequest = new CompleteRequest(
-					new ResourceReference(ResourceReference.TYPE, "db://{database}/{table}"),
-					new CompleteRequest.CompleteArgument("table", ""),
-					new CompleteRequest.CompleteContext(Map.of("database", "users_db")));
+			CompleteRequest tableRequest = CompleteRequest
+				.builder(new ResourceReference("db://{database}/{table}"),
+						new CompleteRequest.CompleteArgument("table", ""))
+				.context(new CompleteRequest.CompleteContext(Map.of("database", "users_db")))
+				.build();
 
 			CompleteResult tableResult = mcpClient.completeCompletion(tableRequest);
 			assertThat(tableResult.completion().values()).containsExactly("users", "sessions", "permissions");
 
 			// Different database gives different tables
-			CompleteRequest tableRequest2 = new CompleteRequest(
-					new ResourceReference(ResourceReference.TYPE, "db://{database}/{table}"),
-					new CompleteRequest.CompleteArgument("table", ""),
-					new CompleteRequest.CompleteContext(Map.of("database", "products_db")));
+			CompleteRequest tableRequest2 = CompleteRequest
+				.builder(new ResourceReference("db://{database}/{table}"),
+						new CompleteRequest.CompleteArgument("table", ""))
+				.context(new CompleteRequest.CompleteContext(Map.of("database", "products_db")))
+				.build();
 
 			CompleteResult tableResult2 = mcpClient.completeCompletion(tableRequest2);
 			assertThat(tableResult2.completion().values()).containsExactly("products", "categories", "inventory");
@@ -282,9 +288,7 @@ class McpCompletionTests {
 			return new CompleteResult(new CompleteResult.CompleteCompletion(List.of(), 0, false));
 		};
 
-		McpSchema.Resource resource = Resource.builder()
-			.uri("db://{database}/{table}")
-			.name("Database Table")
+		McpSchema.Resource resource = Resource.builder("db://{database}/{table}", "Database Table")
 			.description("Resource representing a table in a database")
 			.mimeType("application/json")
 			.size(456L)
@@ -293,30 +297,33 @@ class McpCompletionTests {
 		var mcpServer = McpServer.sync(mcpServerTransportProvider)
 			.capabilities(ServerCapabilities.builder().completions().build())
 			.resources(new McpServerFeatures.SyncResourceSpecification(resource,
-					(exchange, req) -> new ReadResourceResult(List.of())))
+					(exchange, req) -> ReadResourceResult.builder(List.of()).build()))
 			.completions(new McpServerFeatures.SyncCompletionSpecification(
-					new ResourceReference(ResourceReference.TYPE, "db://{database}/{table}"), completionHandler))
+					new ResourceReference("db://{database}/{table}"), completionHandler))
 			.build();
 
-		try (var mcpClient = clientBuilder.clientInfo(new McpSchema.Implementation("Sample" + "client", "0.0.0"))
+		try (var mcpClient = clientBuilder
+			.clientInfo(McpSchema.Implementation.builder("Sample" + "client", "0.0.0").build())
 			.build();) {
 			InitializeResult initResult = mcpClient.initialize();
 			assertThat(initResult).isNotNull();
 
 			// Try to complete table without database context - should raise error
-			CompleteRequest requestWithoutContext = new CompleteRequest(
-					new ResourceReference(ResourceReference.TYPE, "db://{database}/{table}"),
-					new CompleteRequest.CompleteArgument("table", ""));
+			CompleteRequest requestWithoutContext = CompleteRequest
+				.builder(new ResourceReference("db://{database}/{table}"),
+						new CompleteRequest.CompleteArgument("table", ""))
+				.build();
 
 			assertThatExceptionOfType(McpError.class)
 				.isThrownBy(() -> mcpClient.completeCompletion(requestWithoutContext))
 				.withMessageContaining("Please select a database first");
 
 			// Now complete with proper context - should work normally
-			CompleteRequest requestWithContext = new CompleteRequest(
-					new ResourceReference(ResourceReference.TYPE, "db://{database}/{table}"),
-					new CompleteRequest.CompleteArgument("table", ""),
-					new CompleteRequest.CompleteContext(Map.of("database", "test_db")));
+			CompleteRequest requestWithContext = CompleteRequest
+				.builder(new ResourceReference("db://{database}/{table}"),
+						new CompleteRequest.CompleteArgument("table", ""))
+				.context(new CompleteRequest.CompleteContext(Map.of("database", "test_db")))
+				.build();
 
 			CompleteResult resultWithContext = mcpClient.completeCompletion(requestWithContext);
 			assertThat(resultWithContext.completion().values()).containsExactly("users", "orders", "products");
@@ -330,24 +337,26 @@ class McpCompletionTests {
 		BiFunction<McpSyncServerExchange, CompleteRequest, CompleteResult> completionHandler = (exchange,
 				request) -> new CompleteResult(new CompleteResult.CompleteCompletion(List.of("test"), 1, false));
 
-		McpSchema.Prompt prompt = new Prompt("test-prompt", "this is a test prompt", null);
+		McpSchema.Prompt prompt = Prompt.builder("test-prompt").description("this is a test prompt").build();
 
 		var mcpServer = McpServer.sync(mcpServerTransportProvider)
 			.capabilities(ServerCapabilities.builder().completions().build())
 			.prompts(new McpServerFeatures.SyncPromptSpecification(prompt,
 					(mcpSyncServerExchange, getPromptRequest) -> null))
-			.completions(new McpServerFeatures.SyncCompletionSpecification(
-					new PromptReference(PromptReference.TYPE, "test-prompt"), completionHandler))
+			.completions(new McpServerFeatures.SyncCompletionSpecification(new PromptReference("test-prompt"),
+					completionHandler))
 			.build();
 
-		try (var mcpClient = clientBuilder.clientInfo(new McpSchema.Implementation("Sample " + "client", "0.0.0"))
+		try (var mcpClient = clientBuilder
+			.clientInfo(McpSchema.Implementation.builder("Sample " + "client", "0.0.0").build())
 			.build()) {
 			InitializeResult initResult = mcpClient.initialize();
 			assertThat(initResult).isNotNull();
 
 			// try completing an argument knowing that the prompt is not parameterized
-			CompleteRequest request = new CompleteRequest(new PromptReference(PromptReference.TYPE, "test-prompt"),
-					new CompleteRequest.CompleteArgument("arg", "val"));
+			CompleteRequest request = CompleteRequest
+				.builder(new PromptReference("test-prompt"), new CompleteRequest.CompleteArgument("arg", "val"))
+				.build();
 
 			CompleteResult completeResult = mcpClient.completeCompletion(request);
 			assertThat(completeResult.completion().values()).isEmpty();

mcp-test/src/test/java/io/modelcontextprotocol/server/McpServerProtocolVersionTests.java

@@ -20,13 +20,17 @@ import static org.assertj.core.api.Assertions.assertThat;
  */
 class McpServerProtocolVersionTests {
 
-	private static final McpSchema.Implementation SERVER_INFO = new McpSchema.Implementation("test-server", "1.0.0");
+	private static final McpSchema.Implementation SERVER_INFO = McpSchema.Implementation.builder("test-server", "1.0.0")
+		.build();
 
-	private static final McpSchema.Implementation CLIENT_INFO = new McpSchema.Implementation("test-client", "1.0.0");
+	private static final McpSchema.Implementation CLIENT_INFO = McpSchema.Implementation.builder("test-client", "1.0.0")
+		.build();
 
 	private McpSchema.JSONRPCRequest jsonRpcInitializeRequest(String requestId, String protocolVersion) {
-		return new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION, McpSchema.METHOD_INITIALIZE, requestId,
-				new McpSchema.InitializeRequest(protocolVersion, null, CLIENT_INFO));
+		return new McpSchema.JSONRPCRequest(McpSchema.METHOD_INITIALIZE, requestId,
+				McpSchema.InitializeRequest
+					.builder(protocolVersion, McpSchema.ClientCapabilities.builder().build(), CLIENT_INFO)
+					.build());
 	}
 
 	@Test

mcp-test/src/test/java/io/modelcontextprotocol/server/ResourceSubscriptionTests.java

@@ -24,9 +24,11 @@ class ResourceSubscriptionTests {
 
 	private static final String RESOURCE_URI = "test://resource/1";
 
-	private static final McpSchema.Implementation SERVER_INFO = new McpSchema.Implementation("test-server", "1.0.0");
+	private static final McpSchema.Implementation SERVER_INFO = McpSchema.Implementation.builder("test-server", "1.0.0")
+		.build();
 
-	private static final McpSchema.Implementation CLIENT_INFO = new McpSchema.Implementation("test-client", "1.0.0");
+	private static final McpSchema.Implementation CLIENT_INFO = McpSchema.Implementation.builder("test-client", "1.0.0")
+		.build();
 
 	private static McpAsyncServer buildServer(MockMcpServerTransportProvider transportProvider) {
 		return McpServer.async(transportProvider)
@@ -36,24 +38,25 @@ class ResourceSubscriptionTests {
 	}
 
 	private static McpSchema.JSONRPCRequest initRequest() {
-		return new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION, McpSchema.METHOD_INITIALIZE,
-				UUID.randomUUID().toString(),
-				new McpSchema.InitializeRequest(ProtocolVersions.MCP_2025_11_25, null, CLIENT_INFO));
+		return new McpSchema.JSONRPCRequest(McpSchema.METHOD_INITIALIZE, UUID.randomUUID().toString(),
+				McpSchema.InitializeRequest
+					.builder(ProtocolVersions.MCP_2025_11_25, McpSchema.ClientCapabilities.builder().build(),
+							CLIENT_INFO)
+					.build());
 	}
 
 	private static McpSchema.JSONRPCNotification initializedNotification() {
-		return new McpSchema.JSONRPCNotification(McpSchema.JSONRPC_VERSION, McpSchema.METHOD_NOTIFICATION_INITIALIZED,
-				null);
+		return new McpSchema.JSONRPCNotification(McpSchema.METHOD_NOTIFICATION_INITIALIZED);
 	}
 
 	private static McpSchema.JSONRPCRequest subscribeRequest(String uri) {
-		return new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION, McpSchema.METHOD_RESOURCES_SUBSCRIBE,
-				UUID.randomUUID().toString(), new McpSchema.SubscribeRequest(uri));
+		return new McpSchema.JSONRPCRequest(McpSchema.METHOD_RESOURCES_SUBSCRIBE, UUID.randomUUID().toString(),
+				McpSchema.SubscribeRequest.builder(uri).build());
 	}
 
 	private static McpSchema.JSONRPCRequest unsubscribeRequest(String uri) {
-		return new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION, McpSchema.METHOD_RESOURCES_UNSUBSCRIBE,
-				UUID.randomUUID().toString(), new McpSchema.UnsubscribeRequest(uri));
+		return new McpSchema.JSONRPCRequest(McpSchema.METHOD_RESOURCES_UNSUBSCRIBE, UUID.randomUUID().toString(),
+				McpSchema.UnsubscribeRequest.builder(uri).build());
 	}
 
 	@Test

mcp-test/src/test/java/io/modelcontextprotocol/server/ResourceTemplateManagementTests.java

@@ -62,15 +62,13 @@ public class ResourceTemplateManagementTests {
 			.capabilities(ServerCapabilities.builder().resources(true, false).build())
 			.build();
 
-		ResourceTemplate template = ResourceTemplate.builder()
-			.uriTemplate(TEST_TEMPLATE_URI)
-			.name(TEST_TEMPLATE_NAME)
+		ResourceTemplate template = ResourceTemplate.builder(TEST_TEMPLATE_URI, TEST_TEMPLATE_NAME)
 			.description("Test resource template")
 			.mimeType("text/plain")
 			.build();
 
 		McpServerFeatures.AsyncResourceTemplateSpecification specification = new McpServerFeatures.AsyncResourceTemplateSpecification(
-				template, (exchange, req) -> Mono.just(new ReadResourceResult(List.of())));
+				template, (exchange, req) -> Mono.just(ReadResourceResult.builder(List.of()).build()));
 
 		StepVerifier.create(mcpAsyncServer.addResourceTemplate(specification)).verifyComplete();
 	}
@@ -82,15 +80,13 @@ public class ResourceTemplateManagementTests {
 			.serverInfo("test-server", "1.0.0")
 			.build();
 
-		ResourceTemplate template = ResourceTemplate.builder()
-			.uriTemplate(TEST_TEMPLATE_URI)
-			.name(TEST_TEMPLATE_NAME)
+		ResourceTemplate template = ResourceTemplate.builder(TEST_TEMPLATE_URI, TEST_TEMPLATE_NAME)
 			.description("Test resource template")
 			.mimeType("text/plain")
 			.build();
 
 		McpServerFeatures.AsyncResourceTemplateSpecification specification = new McpServerFeatures.AsyncResourceTemplateSpecification(
-				template, (exchange, req) -> Mono.just(new ReadResourceResult(List.of())));
+				template, (exchange, req) -> Mono.just(ReadResourceResult.builder(List.of()).build()));
 
 		StepVerifier.create(serverWithoutResources.addResourceTemplate(specification)).verifyErrorSatisfies(error -> {
 			assertThat(error).isInstanceOf(IllegalStateException.class)
@@ -103,15 +99,13 @@ public class ResourceTemplateManagementTests {
 
 	@Test
 	void testRemoveResourceTemplate() {
-		ResourceTemplate template = ResourceTemplate.builder()
-			.uriTemplate(TEST_TEMPLATE_URI)
-			.name(TEST_TEMPLATE_NAME)
+		ResourceTemplate template = ResourceTemplate.builder(TEST_TEMPLATE_URI, TEST_TEMPLATE_NAME)
 			.description("Test resource template")
 			.mimeType("text/plain")
 			.build();
 
 		McpServerFeatures.AsyncResourceTemplateSpecification specification = new McpServerFeatures.AsyncResourceTemplateSpecification(
-				template, (exchange, req) -> Mono.just(new ReadResourceResult(List.of())));
+				template, (exchange, req) -> Mono.just(ReadResourceResult.builder(List.of()).build()));
 
 		mcpAsyncServer = McpServer.async(mockTransportProvider)
 			.serverInfo("test-server", "1.0.0")
@@ -154,25 +148,21 @@ public class ResourceTemplateManagementTests {
 
 	@Test
 	void testReplaceExistingResourceTemplate() {
-		ResourceTemplate originalTemplate = ResourceTemplate.builder()
-			.uriTemplate(TEST_TEMPLATE_URI)
-			.name(TEST_TEMPLATE_NAME)
+		ResourceTemplate originalTemplate = ResourceTemplate.builder(TEST_TEMPLATE_URI, TEST_TEMPLATE_NAME)
 			.description("Original template")
 			.mimeType("text/plain")
 			.build();
 
-		ResourceTemplate updatedTemplate = ResourceTemplate.builder()
-			.uriTemplate(TEST_TEMPLATE_URI)
-			.name(TEST_TEMPLATE_NAME)
+		ResourceTemplate updatedTemplate = ResourceTemplate.builder(TEST_TEMPLATE_URI, TEST_TEMPLATE_NAME)
 			.description("Updated template")
 			.mimeType("application/json")
 			.build();
 
 		McpServerFeatures.AsyncResourceTemplateSpecification originalSpec = new McpServerFeatures.AsyncResourceTemplateSpecification(
-				originalTemplate, (exchange, req) -> Mono.just(new ReadResourceResult(List.of())));
+				originalTemplate, (exchange, req) -> Mono.just(ReadResourceResult.builder(List.of()).build()));
 
 		McpServerFeatures.AsyncResourceTemplateSpecification updatedSpec = new McpServerFeatures.AsyncResourceTemplateSpecification(
-				updatedTemplate, (exchange, req) -> Mono.just(new ReadResourceResult(List.of())));
+				updatedTemplate, (exchange, req) -> Mono.just(ReadResourceResult.builder(List.of()).build()));
 
 		mcpAsyncServer = McpServer.async(mockTransportProvider)
 			.serverInfo("test-server", "1.0.0")
@@ -190,15 +180,13 @@ public class ResourceTemplateManagementTests {
 
 	@Test
 	void testSyncAddResourceTemplate() {
-		ResourceTemplate template = ResourceTemplate.builder()
-			.uriTemplate(TEST_TEMPLATE_URI)
-			.name(TEST_TEMPLATE_NAME)
+		ResourceTemplate template = ResourceTemplate.builder(TEST_TEMPLATE_URI, TEST_TEMPLATE_NAME)
 			.description("Test resource template")
 			.mimeType("text/plain")
 			.build();
 
 		McpServerFeatures.SyncResourceTemplateSpecification specification = new McpServerFeatures.SyncResourceTemplateSpecification(
-				template, (exchange, req) -> new ReadResourceResult(List.of()));
+				template, (exchange, req) -> ReadResourceResult.builder(List.of()).build());
 
 		var mcpSyncServer = McpServer.sync(mockTransportProvider)
 			.serverInfo("test-server", "1.0.0")
@@ -212,15 +200,13 @@ public class ResourceTemplateManagementTests {
 
 	@Test
 	void testSyncRemoveResourceTemplate() {
-		ResourceTemplate template = ResourceTemplate.builder()
-			.uriTemplate(TEST_TEMPLATE_URI)
-			.name(TEST_TEMPLATE_NAME)
+		ResourceTemplate template = ResourceTemplate.builder(TEST_TEMPLATE_URI, TEST_TEMPLATE_NAME)
 			.description("Test resource template")
 			.mimeType("text/plain")
 			.build();
 
 		McpServerFeatures.SyncResourceTemplateSpecification specification = new McpServerFeatures.SyncResourceTemplateSpecification(
-				template, (exchange, req) -> new ReadResourceResult(List.of()));
+				template, (exchange, req) -> ReadResourceResult.builder(List.of()).build());
 
 		var mcpSyncServer = McpServer.sync(mockTransportProvider)
 			.serverInfo("test-server", "1.0.0")
@@ -239,25 +225,21 @@ public class ResourceTemplateManagementTests {
 
 	@Test
 	void testResourceTemplateMapBasedStorage() {
-		ResourceTemplate template1 = ResourceTemplate.builder()
-			.uriTemplate("test://template1/{id}")
-			.name("template1")
+		ResourceTemplate template1 = ResourceTemplate.builder("test://template1/{id}", "template1")
 			.description("First template")
 			.mimeType("text/plain")
 			.build();
 
-		ResourceTemplate template2 = ResourceTemplate.builder()
-			.uriTemplate("test://template2/{id}")
-			.name("template2")
+		ResourceTemplate template2 = ResourceTemplate.builder("test://template2/{id}", "template2")
 			.description("Second template")
 			.mimeType("application/json")
 			.build();
 
 		McpServerFeatures.AsyncResourceTemplateSpecification spec1 = new McpServerFeatures.AsyncResourceTemplateSpecification(
-				template1, (exchange, req) -> Mono.just(new ReadResourceResult(List.of())));
+				template1, (exchange, req) -> Mono.just(ReadResourceResult.builder(List.of()).build()));
 
 		McpServerFeatures.AsyncResourceTemplateSpecification spec2 = new McpServerFeatures.AsyncResourceTemplateSpecification(
-				template2, (exchange, req) -> Mono.just(new ReadResourceResult(List.of())));
+				template2, (exchange, req) -> Mono.just(ReadResourceResult.builder(List.of()).build()));
 
 		mcpAsyncServer = McpServer.async(mockTransportProvider)
 			.serverInfo("test-server", "1.0.0")
@@ -274,15 +256,13 @@ public class ResourceTemplateManagementTests {
 	@Test
 	void testResourceTemplateBuilderWithMap() {
 		// Test that the new Map-based builder methods work correctly
-		ResourceTemplate template = ResourceTemplate.builder()
-			.uriTemplate(TEST_TEMPLATE_URI)
-			.name(TEST_TEMPLATE_NAME)
+		ResourceTemplate template = ResourceTemplate.builder(TEST_TEMPLATE_URI, TEST_TEMPLATE_NAME)
 			.description("Test resource template")
 			.mimeType("text/plain")
 			.build();
 
 		McpServerFeatures.AsyncResourceTemplateSpecification specification = new McpServerFeatures.AsyncResourceTemplateSpecification(
-				template, (exchange, req) -> Mono.just(new ReadResourceResult(List.of())));
+				template, (exchange, req) -> Mono.just(ReadResourceResult.builder(List.of()).build()));
 
 		// Test varargs builder method
 		assertThatCode(() -> {

mcp-test/src/test/java/io/modelcontextprotocol/server/ToolInputValidationIntegrationTests.java

@@ -49,9 +49,11 @@ class ToolInputValidationIntegrationTests {
 
 	private static final String TOOL_NAME = "test-tool";
 
-	private static final McpSchema.JsonSchema INPUT_SCHEMA = new McpSchema.JsonSchema("object",
-			Map.of("name", Map.of("type", "string"), "age", Map.of("type", "integer", "minimum", 0)),
-			List.of("name", "age"), null, null, null);
+	private static final McpSchema.JsonSchema INPUT_SCHEMA = McpSchema.JsonSchema.builder()
+		.type("object")
+		.properties(Map.of("name", Map.of("type", "string"), "age", Map.of("type", "integer", "minimum", 0)))
+		.required(List.of("name", "age"))
+		.build();
 
 	private static final McpTransportContextExtractor<HttpServletRequest> TEST_CONTEXT_EXTRACTOR = (
 			r) -> McpTransportContext.create(Map.of("important", "value"));
@@ -123,34 +125,26 @@ class ToolInputValidationIntegrationTests {
 	}
 
 	private McpServerFeatures.SyncToolSpecification createSyncTool() {
-		Tool tool = Tool.builder()
-			.name(TOOL_NAME)
-			.description("Test tool with schema")
-			.inputSchema(INPUT_SCHEMA)
-			.build();
+		Tool tool = Tool.builder(TOOL_NAME).inputSchema(INPUT_SCHEMA).description("Test tool with schema").build();
 
 		return McpServerFeatures.SyncToolSpecification.builder().tool(tool).callHandler((exchange, request) -> {
 			String name = (String) request.arguments().get("name");
 			Integer age = ((Number) request.arguments().get("age")).intValue();
 			return CallToolResult.builder()
-				.content(List.of(new TextContent("Hello " + name + ", age " + age)))
+				.content(List.of(TextContent.builder("Hello " + name + ", age " + age).build()))
 				.isError(false)
 				.build();
 		}).build();
 	}
 
 	private McpServerFeatures.AsyncToolSpecification createAsyncTool() {
-		Tool tool = Tool.builder()
-			.name(TOOL_NAME)
-			.description("Test tool with schema")
-			.inputSchema(INPUT_SCHEMA)
-			.build();
+		Tool tool = Tool.builder(TOOL_NAME).inputSchema(INPUT_SCHEMA).description("Test tool with schema").build();
 
 		return McpServerFeatures.AsyncToolSpecification.builder().tool(tool).callHandler((exchange, request) -> {
 			String name = (String) request.arguments().get("name");
 			Integer age = ((Number) request.arguments().get("age")).intValue();
 			return Mono.just(CallToolResult.builder()
-				.content(List.of(new TextContent("Hello " + name + ", age " + age)))
+				.content(List.of(TextContent.builder("Hello " + name + ", age " + age).build()))
 				.isError(false)
 				.build());
 		}).build();
@@ -162,9 +156,10 @@ class ToolInputValidationIntegrationTests {
 			String expectedOutput) {
 		Object server = createServer(serverType, validationEnabled);
 
-		try (var client = clientBuilder.clientInfo(new McpSchema.Implementation("test-client", "1.0.0")).build()) {
+		try (var client = clientBuilder.clientInfo(McpSchema.Implementation.builder("test-client", "1.0.0").build())
+			.build()) {
 			client.initialize();
-			CallToolResult result = client.callTool(new CallToolRequest(TOOL_NAME, input));
+			CallToolResult result = client.callTool(CallToolRequest.builder(TOOL_NAME).arguments(input).build());
 
 			assertThat(result.isError()).isFalse();
 			assertThat(((TextContent) result.content().get(0)).text()).isEqualTo(expectedOutput);
@@ -180,9 +175,10 @@ class ToolInputValidationIntegrationTests {
 			String expectedErrorSubstring) {
 		Object server = createServerWithDefaultValidation(serverType);
 
-		try (var client = clientBuilder.clientInfo(new McpSchema.Implementation("test-client", "1.0.0")).build()) {
+		try (var client = clientBuilder.clientInfo(McpSchema.Implementation.builder("test-client", "1.0.0").build())
+			.build()) {
 			client.initialize();
-			CallToolResult result = client.callTool(new CallToolRequest(TOOL_NAME, input));
+			CallToolResult result = client.callTool(CallToolRequest.builder(TOOL_NAME).arguments(input).build());
 
 			assertThat(result.isError()).isTrue();
 			String errorMessage = ((TextContent) result.content().get(0)).text();
@@ -199,13 +195,14 @@ class ToolInputValidationIntegrationTests {
 			String ignored) {
 		Object server = createServer(serverType, false);
 
-		try (var client = clientBuilder.clientInfo(new McpSchema.Implementation("test-client", "1.0.0")).build()) {
+		try (var client = clientBuilder.clientInfo(McpSchema.Implementation.builder("test-client", "1.0.0").build())
+			.build()) {
 			client.initialize();
 			// Invalid input should pass through when validation is disabled
 			// The tool handler will fail, but that's expected - we're testing validation
 			// is skipped
 			try {
-				client.callTool(new CallToolRequest(TOOL_NAME, input));
+				client.callTool(CallToolRequest.builder(TOOL_NAME).arguments(input).build());
 			}
 			catch (Exception e) {
 				// Expected - tool handler fails on invalid input, but validation didn't

mcp-test/src/test/java/io/modelcontextprotocol/server/transport/HttpServletSseServerCustomContextPathTests.java

@@ -78,7 +78,7 @@ class HttpServletSseServerCustomContextPathTests {
 	void testCustomContextPath() {
 		var server = McpServer.async(mcpServerTransportProvider).serverInfo("test-server", "1.0.0").build();
 		try (//@formatter:off
-			var client = clientBuilder.clientInfo(new McpSchema.Implementation("Sample " + "client", "0.0.0")) .build()) { //@formatter:on
+			var client = clientBuilder.clientInfo(McpSchema.Implementation.builder("Sample " + "client", "0.0.0").build()) .build()) { //@formatter:on
 
 			assertThat(client.initialize()).isNotNull();
 		}

mcp-test/src/test/java/io/modelcontextprotocol/spec/CompleteReferenceJsonTests.java

@@ -7,6 +7,7 @@ package io.modelcontextprotocol.spec;
 import static io.modelcontextprotocol.util.McpJsonMapperUtils.JSON_MAPPER;
 import static net.javacrumbs.jsonunit.assertj.JsonAssertions.assertThatJson;
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 import java.io.IOException;
 
@@ -50,7 +51,7 @@ class CompleteReferenceJsonTests {
 		McpSchema.CompleteRequest req = mapper.readValue(json, McpSchema.CompleteRequest.class);
 
 		assertThat(req.ref()).isInstanceOf(McpSchema.PromptReference.class);
-		assertThat(req.ref().identifier()).isEqualTo("my-prompt");
+		assertThat(((McpSchema.PromptReference) req.ref()).name()).isEqualTo("my-prompt");
 		assertThat(req.argument().name()).isEqualTo("lang");
 		assertThat(req.argument().value()).isEqualTo("java");
 	}
@@ -64,7 +65,7 @@ class CompleteReferenceJsonTests {
 		McpSchema.CompleteRequest req = mapper.readValue(json, McpSchema.CompleteRequest.class);
 
 		assertThat(req.ref()).isInstanceOf(McpSchema.ResourceReference.class);
-		assertThat(req.ref().identifier()).isEqualTo("file:///src/Foo.java");
+		assertThat(((McpSchema.ResourceReference) req.ref()).uri()).isEqualTo("file:///src/Foo.java");
 	}
 
 	@Test
@@ -79,7 +80,21 @@ class CompleteReferenceJsonTests {
 		});
 
 		assertThat(req.ref()).isInstanceOf(McpSchema.PromptReference.class);
-		assertThat(req.ref().identifier()).isEqualTo("my-prompt");
+		assertThat(((McpSchema.PromptReference) req.ref()).name()).isEqualTo("my-prompt");
+	}
+
+	@Test
+	void completeRequestMissingRefFailsToInstantiate() throws IOException {
+		String json = """
+				{"argument":{"name":"lang","value":"java"}}
+				""";
+
+		// This is the real in-process path: params arrives as a Map from JSON-RPC
+		Object paramsMap = mapper.readValue(json, Object.class);
+
+		assertThatThrownBy(() -> mapper.convertValue(paramsMap, new TypeRef<McpSchema.CompleteRequest>() {
+		})).hasMessageContaining("ref must not be null");
+
 	}
 
 	@Test

mcp-test/src/test/java/io/modelcontextprotocol/spec/ContentJsonTests.java

@@ -24,7 +24,7 @@ class ContentJsonTests {
 
 	@Test
 	void textContentHasExactlyOneTypeProperty() throws IOException {
-		McpSchema.TextContent content = new McpSchema.TextContent("hello");
+		McpSchema.TextContent content = McpSchema.TextContent.builder("hello").build();
 		String json = mapper.writeValueAsString(content);
 
 		assertExactlyOneTypeProperty(json);
@@ -34,7 +34,7 @@ class ContentJsonTests {
 
 	@Test
 	void imageContentHasExactlyOneTypeProperty() throws IOException {
-		McpSchema.ImageContent content = new McpSchema.ImageContent(null, "base64data", "image/png");
+		McpSchema.ImageContent content = McpSchema.ImageContent.builder("base64data", "image/png").build();
 		String json = mapper.writeValueAsString(content);
 
 		assertExactlyOneTypeProperty(json);
@@ -43,7 +43,7 @@ class ContentJsonTests {
 
 	@Test
 	void audioContentHasExactlyOneTypeProperty() throws IOException {
-		McpSchema.AudioContent content = new McpSchema.AudioContent(null, "base64data", "audio/mp3");
+		McpSchema.AudioContent content = McpSchema.AudioContent.builder("base64data", "audio/mp3").build();
 		String json = mapper.writeValueAsString(content);
 
 		assertExactlyOneTypeProperty(json);
@@ -52,7 +52,7 @@ class ContentJsonTests {
 
 	@Test
 	void textContentRoundTrip() throws IOException {
-		McpSchema.TextContent original = new McpSchema.TextContent("round-trip");
+		McpSchema.TextContent original = McpSchema.TextContent.builder("round-trip").build();
 		String json = mapper.writeValueAsString(original);
 
 		McpSchema.Content decoded = mapper.readValue(json, McpSchema.Content.class);

mcp-test/src/test/java/io/modelcontextprotocol/spec/McpSchemaTests.java

@@ -34,7 +34,7 @@ public class McpSchemaTests {
 
 	@Test
 	void testTextContent() throws Exception {
-		McpSchema.TextContent test = new McpSchema.TextContent("XXX");
+		McpSchema.TextContent test = McpSchema.TextContent.builder("XXX").build();
 		String value = JSON_MAPPER.writeValueAsString(test);
 
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -73,7 +73,7 @@ public class McpSchemaTests {
 
 	@Test
 	void testImageContent() throws Exception {
-		McpSchema.ImageContent test = new McpSchema.ImageContent(null, "base64encodeddata", "image/png");
+		McpSchema.ImageContent test = McpSchema.ImageContent.builder("base64encodeddata", "image/png").build();
 		String value = JSON_MAPPER.writeValueAsString(test);
 
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -97,7 +97,7 @@ public class McpSchemaTests {
 
 	@Test
 	void testAudioContent() throws Exception {
-		McpSchema.AudioContent audioContent = new McpSchema.AudioContent(null, "base64encodeddata", "audio/wav");
+		McpSchema.AudioContent audioContent = McpSchema.AudioContent.builder("base64encodeddata", "audio/wav").build();
 		String value = JSON_MAPPER.writeValueAsString(audioContent);
 
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -121,11 +121,15 @@ public class McpSchemaTests {
 
 	@Test
 	void testCreateMessageRequestWithMeta() throws Exception {
-		McpSchema.TextContent content = new McpSchema.TextContent("User message");
-		McpSchema.SamplingMessage message = new McpSchema.SamplingMessage(McpSchema.Role.USER, content);
-		McpSchema.ModelHint hint = new McpSchema.ModelHint("gpt-4");
-		McpSchema.ModelPreferences preferences = new McpSchema.ModelPreferences(Collections.singletonList(hint), 0.3,
-				0.7, 0.9);
+		McpSchema.TextContent content = McpSchema.TextContent.builder("User message").build();
+		McpSchema.SamplingMessage message = McpSchema.SamplingMessage.builder(McpSchema.Role.USER, content).build();
+		McpSchema.ModelHint hint = McpSchema.ModelHint.of("gpt-4");
+		McpSchema.ModelPreferences preferences = McpSchema.ModelPreferences.builder()
+			.hints(Collections.singletonList(hint))
+			.costPriority(0.3)
+			.speedPriority(0.7)
+			.intelligencePriority(0.9)
+			.build();
 
 		Map<String, Object> metadata = new HashMap<>();
 		metadata.put("session", "test-session");
@@ -133,13 +137,12 @@ public class McpSchemaTests {
 		Map<String, Object> meta = new HashMap<>();
 		meta.put("progressToken", "create-message-token-456");
 
-		McpSchema.CreateMessageRequest request = McpSchema.CreateMessageRequest.builder()
-			.messages(Collections.singletonList(message))
+		McpSchema.CreateMessageRequest request = McpSchema.CreateMessageRequest
+			.builder(Collections.singletonList(message), 1000)
 			.modelPreferences(preferences)
 			.systemPrompt("You are a helpful assistant")
 			.includeContext(McpSchema.CreateMessageRequest.ContextInclusionStrategy.THIS_SERVER)
 			.temperature(0.7)
-			.maxTokens(1000)
 			.stopSequences(Arrays.asList("STOP", "END"))
 			.metadata(metadata)
 			.meta(meta)
@@ -158,10 +161,12 @@ public class McpSchemaTests {
 
 	@Test
 	void testEmbeddedResource() throws Exception {
-		McpSchema.TextResourceContents resourceContents = new McpSchema.TextResourceContents("resource://test",
-				"text/plain", "Sample resource content");
+		McpSchema.TextResourceContents resourceContents = McpSchema.TextResourceContents
+			.builder("resource://test", "Sample resource content")
+			.mimeType("text/plain")
+			.build();
 
-		McpSchema.EmbeddedResource test = new McpSchema.EmbeddedResource(null, resourceContents);
+		McpSchema.EmbeddedResource test = McpSchema.EmbeddedResource.builder(resourceContents).build();
 
 		String value = JSON_MAPPER.writeValueAsString(test);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -189,10 +194,12 @@ public class McpSchemaTests {
 
 	@Test
 	void testEmbeddedResourceWithBlobContents() throws Exception {
-		McpSchema.BlobResourceContents resourceContents = new McpSchema.BlobResourceContents("resource://test",
-				"application/octet-stream", "base64encodedblob");
+		McpSchema.BlobResourceContents resourceContents = McpSchema.BlobResourceContents
+			.builder("resource://test", "base64encodedblob")
+			.mimeType("application/octet-stream")
+			.build();
 
-		McpSchema.EmbeddedResource test = new McpSchema.EmbeddedResource(null, resourceContents);
+		McpSchema.EmbeddedResource test = McpSchema.EmbeddedResource.builder(resourceContents).build();
 
 		String value = JSON_MAPPER.writeValueAsString(test);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -221,9 +228,14 @@ public class McpSchemaTests {
 
 	@Test
 	void testResourceLink() throws Exception {
-		McpSchema.ResourceLink resourceLink = new McpSchema.ResourceLink("main.rs", "Main file",
-				"file:///project/src/main.rs", "Primary application entry point", "text/x-rust", null, null,
-				Map.of("metaKey", "metaValue"));
+		McpSchema.ResourceLink resourceLink = McpSchema.ResourceLink.builder()
+			.name("main.rs")
+			.title("Main file")
+			.uri("file:///project/src/main.rs")
+			.description("Primary application entry point")
+			.mimeType("text/x-rust")
+			.meta(Map.of("metaKey", "metaValue"))
+			.build();
 		String value = JSON_MAPPER.writeValueAsString(resourceLink);
 
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -256,8 +268,7 @@ public class McpSchemaTests {
 		Map<String, Object> params = new HashMap<>();
 		params.put("key", "value");
 
-		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION, "method_name", 1,
-				params);
+		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest("method_name", 1, params);
 
 		String value = JSON_MAPPER.writeValueAsString(request);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -272,8 +283,7 @@ public class McpSchemaTests {
 		Map<String, Object> params = new HashMap<>();
 		params.put("key", "value");
 
-		McpSchema.JSONRPCNotification notification = new McpSchema.JSONRPCNotification(McpSchema.JSONRPC_VERSION,
-				"notification_method", params);
+		McpSchema.JSONRPCNotification notification = new McpSchema.JSONRPCNotification("notification_method", params);
 
 		String value = JSON_MAPPER.writeValueAsString(notification);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -288,7 +298,7 @@ public class McpSchemaTests {
 		Map<String, Object> result = new HashMap<>();
 		result.put("result_key", "result_value");
 
-		McpSchema.JSONRPCResponse response = new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION, 1, result, null);
+		McpSchema.JSONRPCResponse response = McpSchema.JSONRPCResponse.result(1, result);
 
 		String value = JSON_MAPPER.writeValueAsString(response);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -301,9 +311,9 @@ public class McpSchemaTests {
 	@Test
 	void testJSONRPCResponseWithError() throws Exception {
 		McpSchema.JSONRPCResponse.JSONRPCError error = new McpSchema.JSONRPCResponse.JSONRPCError(
-				McpSchema.ErrorCodes.INVALID_REQUEST, "Invalid request", null);
+				McpSchema.ErrorCodes.INVALID_REQUEST, "Invalid request");
 
-		McpSchema.JSONRPCResponse response = new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION, 1, null, error);
+		McpSchema.JSONRPCResponse response = McpSchema.JSONRPCResponse.error(1, error);
 
 		String value = JSON_MAPPER.writeValueAsString(response);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -322,11 +332,13 @@ public class McpSchemaTests {
 			.sampling()
 			.build();
 
-		McpSchema.Implementation clientInfo = new McpSchema.Implementation("test-client", "1.0.0");
+		McpSchema.Implementation clientInfo = McpSchema.Implementation.builder("test-client", "1.0.0").build();
 		Map<String, Object> meta = Map.of("metaKey", "metaValue");
 
-		McpSchema.InitializeRequest request = new McpSchema.InitializeRequest(ProtocolVersions.MCP_2024_11_05,
-				capabilities, clientInfo, meta);
+		McpSchema.InitializeRequest request = McpSchema.InitializeRequest
+			.builder(ProtocolVersions.MCP_2024_11_05, capabilities, clientInfo)
+			.meta(meta)
+			.build();
 
 		String value = JSON_MAPPER.writeValueAsString(request);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -346,10 +358,12 @@ public class McpSchemaTests {
 			.tools(true)
 			.build();
 
-		McpSchema.Implementation serverInfo = new McpSchema.Implementation("test-server", "1.0.0");
+		McpSchema.Implementation serverInfo = McpSchema.Implementation.builder("test-server", "1.0.0").build();
 
-		McpSchema.InitializeResult result = new McpSchema.InitializeResult(ProtocolVersions.MCP_2024_11_05,
-				capabilities, serverInfo, "Server initialized successfully");
+		McpSchema.InitializeResult result = McpSchema.InitializeResult
+			.builder(ProtocolVersions.MCP_2024_11_05, capabilities, serverInfo)
+			.instructions("Server initialized successfully")
+			.build();
 
 		String value = JSON_MAPPER.writeValueAsString(result);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -364,12 +378,12 @@ public class McpSchemaTests {
 
 	@Test
 	void testResource() throws Exception {
-		McpSchema.Annotations annotations = new McpSchema.Annotations(
-				Arrays.asList(McpSchema.Role.USER, McpSchema.Role.ASSISTANT), 0.8);
+		McpSchema.Annotations annotations = McpSchema.Annotations.builder()
+			.audience(Arrays.asList(McpSchema.Role.USER, McpSchema.Role.ASSISTANT))
+			.priority(0.8)
+			.build();
 
-		McpSchema.Resource resource = McpSchema.Resource.builder()
-			.uri("resource://test")
-			.name("Test Resource")
+		McpSchema.Resource resource = McpSchema.Resource.builder("resource://test", "Test Resource")
 			.description("A test resource")
 			.mimeType("text/plain")
 			.annotations(annotations)
@@ -386,12 +400,12 @@ public class McpSchemaTests {
 
 	@Test
 	void testResourceBuilder() throws Exception {
-		McpSchema.Annotations annotations = new McpSchema.Annotations(
-				Arrays.asList(McpSchema.Role.USER, McpSchema.Role.ASSISTANT), 0.8);
+		McpSchema.Annotations annotations = McpSchema.Annotations.builder()
+			.audience(Arrays.asList(McpSchema.Role.USER, McpSchema.Role.ASSISTANT))
+			.priority(0.8)
+			.build();
 
-		McpSchema.Resource resource = McpSchema.Resource.builder()
-			.uri("resource://test")
-			.name("Test Resource")
+		McpSchema.Resource resource = McpSchema.Resource.builder("resource://test", "Test Resource")
 			.description("A test resource")
 			.mimeType("text/plain")
 			.size(256L)
@@ -410,41 +424,32 @@ public class McpSchemaTests {
 
 	@Test
 	void testResourceBuilderUriRequired() {
-		McpSchema.Annotations annotations = new McpSchema.Annotations(
-				Arrays.asList(McpSchema.Role.USER, McpSchema.Role.ASSISTANT), 0.8);
-
-		McpSchema.Resource.Builder resourceBuilder = McpSchema.Resource.builder()
-			.name("Test Resource")
-			.description("A test resource")
-			.mimeType("text/plain")
-			.size(256L)
-			.annotations(annotations);
-
-		assertThatThrownBy(resourceBuilder::build).isInstanceOf(java.lang.IllegalArgumentException.class);
+		assertThatThrownBy(() -> McpSchema.Resource.builder(null, "Test Resource"))
+			.isInstanceOf(java.lang.IllegalArgumentException.class);
 	}
 
 	@Test
 	void testResourceBuilderNameRequired() {
-		McpSchema.Annotations annotations = new McpSchema.Annotations(
-				Arrays.asList(McpSchema.Role.USER, McpSchema.Role.ASSISTANT), 0.8);
-
-		McpSchema.Resource.Builder resourceBuilder = McpSchema.Resource.builder()
-			.uri("resource://test")
-			.description("A test resource")
-			.mimeType("text/plain")
-			.size(256L)
-			.annotations(annotations);
-
-		assertThatThrownBy(resourceBuilder::build).isInstanceOf(java.lang.IllegalArgumentException.class);
+		assertThatThrownBy(() -> McpSchema.Resource.builder("resource://test", null))
+			.isInstanceOf(java.lang.IllegalArgumentException.class);
 	}
 
 	@Test
 	void testResourceTemplate() throws Exception {
-		McpSchema.Annotations annotations = new McpSchema.Annotations(Arrays.asList(McpSchema.Role.USER), 0.5);
+		McpSchema.Annotations annotations = McpSchema.Annotations.builder()
+			.audience(Arrays.asList(McpSchema.Role.USER))
+			.priority(0.5)
+			.build();
 		Map<String, Object> meta = Map.of("metaKey", "metaValue");
 
-		McpSchema.ResourceTemplate template = new McpSchema.ResourceTemplate("resource://{param}/test", "Test Template",
-				"Test Template", "A test resource template", "text/plain", annotations, meta);
+		McpSchema.ResourceTemplate template = McpSchema.ResourceTemplate
+			.builder("resource://{param}/test", "Test Template")
+			.title("Test Template")
+			.description("A test resource template")
+			.mimeType("text/plain")
+			.annotations(annotations)
+			.meta(meta)
+			.build();
 
 		String value = JSON_MAPPER.writeValueAsString(template);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -457,24 +462,23 @@ public class McpSchemaTests {
 
 	@Test
 	void testListResourcesResult() throws Exception {
-		McpSchema.Resource resource1 = McpSchema.Resource.builder()
-			.uri("resource://test1")
-			.name("Test Resource 1")
+		McpSchema.Resource resource1 = McpSchema.Resource.builder("resource://test1", "Test Resource 1")
 			.description("First test resource")
 			.mimeType("text/plain")
 			.build();
 
-		McpSchema.Resource resource2 = McpSchema.Resource.builder()
-			.uri("resource://test2")
-			.name("Test Resource 2")
+		McpSchema.Resource resource2 = McpSchema.Resource.builder("resource://test2", "Test Resource 2")
 			.description("Second test resource")
 			.mimeType("application/json")
 			.build();
 
 		Map<String, Object> meta = Map.of("metaKey", "metaValue");
 
-		McpSchema.ListResourcesResult result = new McpSchema.ListResourcesResult(Arrays.asList(resource1, resource2),
-				"next-cursor", meta);
+		McpSchema.ListResourcesResult result = McpSchema.ListResourcesResult
+			.builder(Arrays.asList(resource1, resource2))
+			.nextCursor("next-cursor")
+			.meta(meta)
+			.build();
 
 		String value = JSON_MAPPER.writeValueAsString(result);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -487,14 +491,24 @@ public class McpSchemaTests {
 
 	@Test
 	void testListResourceTemplatesResult() throws Exception {
-		McpSchema.ResourceTemplate template1 = new McpSchema.ResourceTemplate("resource://{param}/test1",
-				"Test Template 1", "Test Template 1", "First test template", "text/plain", null);
+		McpSchema.ResourceTemplate template1 = McpSchema.ResourceTemplate
+			.builder("resource://{param}/test1", "Test Template 1")
+			.title("Test Template 1")
+			.description("First test template")
+			.mimeType("text/plain")
+			.build();
 
-		McpSchema.ResourceTemplate template2 = new McpSchema.ResourceTemplate("resource://{param}/test2",
-				"Test Template 2", "Test Template 2", "Second test template", "application/json", null);
+		McpSchema.ResourceTemplate template2 = McpSchema.ResourceTemplate
+			.builder("resource://{param}/test2", "Test Template 2")
+			.title("Test Template 2")
+			.description("Second test template")
+			.mimeType("application/json")
+			.build();
 
-		McpSchema.ListResourceTemplatesResult result = new McpSchema.ListResourceTemplatesResult(
-				Arrays.asList(template1, template2), "next-cursor");
+		McpSchema.ListResourceTemplatesResult result = McpSchema.ListResourceTemplatesResult
+			.builder(Arrays.asList(template1, template2))
+			.nextCursor("next-cursor")
+			.build();
 
 		String value = JSON_MAPPER.writeValueAsString(result);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -507,8 +521,9 @@ public class McpSchemaTests {
 
 	@Test
 	void testReadResourceRequest() throws Exception {
-		McpSchema.ReadResourceRequest request = new McpSchema.ReadResourceRequest("resource://test",
-				Map.of("metaKey", "metaValue"));
+		McpSchema.ReadResourceRequest request = McpSchema.ReadResourceRequest.builder("resource://test")
+			.meta(Map.of("metaKey", "metaValue"))
+			.build();
 
 		String value = JSON_MAPPER.writeValueAsString(request);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -523,7 +538,9 @@ public class McpSchemaTests {
 		Map<String, Object> meta = new HashMap<>();
 		meta.put("progressToken", "read-resource-token-123");
 
-		McpSchema.ReadResourceRequest request = new McpSchema.ReadResourceRequest("resource://test", meta);
+		McpSchema.ReadResourceRequest request = McpSchema.ReadResourceRequest.builder("resource://test")
+			.meta(meta)
+			.build();
 
 		String value = JSON_MAPPER.writeValueAsString(request);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -550,14 +567,19 @@ public class McpSchemaTests {
 
 	@Test
 	void testReadResourceResult() throws Exception {
-		McpSchema.TextResourceContents contents1 = new McpSchema.TextResourceContents("resource://test1", "text/plain",
-				"Sample text content");
+		McpSchema.TextResourceContents contents1 = McpSchema.TextResourceContents
+			.builder("resource://test1", "Sample text content")
+			.mimeType("text/plain")
+			.build();
 
-		McpSchema.BlobResourceContents contents2 = new McpSchema.BlobResourceContents("resource://test2",
-				"application/octet-stream", "base64encodedblob");
+		McpSchema.BlobResourceContents contents2 = McpSchema.BlobResourceContents
+			.builder("resource://test2", "base64encodedblob")
+			.mimeType("application/octet-stream")
+			.build();
 
-		McpSchema.ReadResourceResult result = new McpSchema.ReadResourceResult(Arrays.asList(contents1, contents2),
-				Map.of("metaKey", "metaValue"));
+		McpSchema.ReadResourceResult result = McpSchema.ReadResourceResult.builder(Arrays.asList(contents1, contents2))
+			.meta(Map.of("metaKey", "metaValue"))
+			.build();
 
 		String value = JSON_MAPPER.writeValueAsString(result);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -572,13 +594,24 @@ public class McpSchemaTests {
 
 	@Test
 	void testPrompt() throws Exception {
-		McpSchema.PromptArgument arg1 = new McpSchema.PromptArgument("arg1", "First argument", "First argument", true);
+		McpSchema.PromptArgument arg1 = McpSchema.PromptArgument.builder("arg1")
+			.title("First argument")
+			.description("First argument")
+			.required(true)
+			.build();
 
-		McpSchema.PromptArgument arg2 = new McpSchema.PromptArgument("arg2", "Second argument", "Second argument",
-				false);
+		McpSchema.PromptArgument arg2 = McpSchema.PromptArgument.builder("arg2")
+			.title("Second argument")
+			.description("Second argument")
+			.required(false)
+			.build();
 
-		McpSchema.Prompt prompt = new McpSchema.Prompt("test-prompt", "Test Prompt", "A test prompt",
-				Arrays.asList(arg1, arg2), Map.of("metaKey", "metaValue"));
+		McpSchema.Prompt prompt = McpSchema.Prompt.builder("test-prompt")
+			.title("Test Prompt")
+			.description("A test prompt")
+			.arguments(Arrays.asList(arg1, arg2))
+			.meta(Map.of("metaKey", "metaValue"))
+			.build();
 
 		String value = JSON_MAPPER.writeValueAsString(prompt);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -591,9 +624,9 @@ public class McpSchemaTests {
 
 	@Test
 	void testPromptMessage() throws Exception {
-		McpSchema.TextContent content = new McpSchema.TextContent("Hello, world!");
+		McpSchema.TextContent content = McpSchema.TextContent.builder("Hello, world!").build();
 
-		McpSchema.PromptMessage message = new McpSchema.PromptMessage(McpSchema.Role.USER, content);
+		McpSchema.PromptMessage message = McpSchema.PromptMessage.builder(McpSchema.Role.USER, content).build();
 
 		String value = JSON_MAPPER.writeValueAsString(message);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -605,16 +638,27 @@ public class McpSchemaTests {
 
 	@Test
 	void testListPromptsResult() throws Exception {
-		McpSchema.PromptArgument arg = new McpSchema.PromptArgument("arg", "Argument", "An argument", true);
+		McpSchema.PromptArgument arg = McpSchema.PromptArgument.builder("arg")
+			.title("Argument")
+			.description("An argument")
+			.required(true)
+			.build();
 
-		McpSchema.Prompt prompt1 = new McpSchema.Prompt("prompt1", "First prompt", "First prompt",
-				Collections.singletonList(arg));
+		McpSchema.Prompt prompt1 = McpSchema.Prompt.builder("prompt1")
+			.title("First prompt")
+			.description("First prompt")
+			.arguments(Collections.singletonList(arg))
+			.build();
 
-		McpSchema.Prompt prompt2 = new McpSchema.Prompt("prompt2", "Second prompt", "Second prompt",
-				Collections.emptyList());
+		McpSchema.Prompt prompt2 = McpSchema.Prompt.builder("prompt2")
+			.title("Second prompt")
+			.description("Second prompt")
+			.arguments(Collections.emptyList())
+			.build();
 
-		McpSchema.ListPromptsResult result = new McpSchema.ListPromptsResult(Arrays.asList(prompt1, prompt2),
-				"next-cursor");
+		McpSchema.ListPromptsResult result = McpSchema.ListPromptsResult.builder(Arrays.asList(prompt1, prompt2))
+			.nextCursor("next-cursor")
+			.build();
 
 		String value = JSON_MAPPER.writeValueAsString(result);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -631,7 +675,9 @@ public class McpSchemaTests {
 		arguments.put("arg1", "value1");
 		arguments.put("arg2", 42);
 
-		McpSchema.GetPromptRequest request = new McpSchema.GetPromptRequest("test-prompt", arguments);
+		McpSchema.GetPromptRequest request = McpSchema.GetPromptRequest.builder("test-prompt")
+			.arguments(arguments)
+			.build();
 
 		assertThat(JSON_MAPPER.readValue("""
 				{"name":"test-prompt","arguments":{"arg1":"value1","arg2":42}}""", McpSchema.GetPromptRequest.class))
@@ -647,7 +693,10 @@ public class McpSchemaTests {
 		Map<String, Object> meta = new HashMap<>();
 		meta.put("progressToken", "token123");
 
-		McpSchema.GetPromptRequest request = new McpSchema.GetPromptRequest("test-prompt", arguments, meta);
+		McpSchema.GetPromptRequest request = McpSchema.GetPromptRequest.builder("test-prompt")
+			.arguments(arguments)
+			.meta(meta)
+			.build();
 
 		String value = JSON_MAPPER.writeValueAsString(request);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -664,15 +713,16 @@ public class McpSchemaTests {
 
 	@Test
 	void testGetPromptResult() throws Exception {
-		McpSchema.TextContent content1 = new McpSchema.TextContent("System message");
-		McpSchema.TextContent content2 = new McpSchema.TextContent("User message");
+		McpSchema.TextContent content1 = McpSchema.TextContent.builder("System message").build();
+		McpSchema.TextContent content2 = McpSchema.TextContent.builder("User message").build();
 
-		McpSchema.PromptMessage message1 = new McpSchema.PromptMessage(McpSchema.Role.ASSISTANT, content1);
+		McpSchema.PromptMessage message1 = McpSchema.PromptMessage.builder(McpSchema.Role.ASSISTANT, content1).build();
 
-		McpSchema.PromptMessage message2 = new McpSchema.PromptMessage(McpSchema.Role.USER, content2);
+		McpSchema.PromptMessage message2 = McpSchema.PromptMessage.builder(McpSchema.Role.USER, content2).build();
 
-		McpSchema.GetPromptResult result = new McpSchema.GetPromptResult("A test prompt result",
-				Arrays.asList(message1, message2));
+		McpSchema.GetPromptResult result = McpSchema.GetPromptResult.builder(Arrays.asList(message1, message2))
+			.description("A test prompt result")
+			.build();
 
 		String value = JSON_MAPPER.writeValueAsString(result);
 
@@ -793,10 +843,8 @@ public class McpSchemaTests {
 				}
 				""";
 
-		McpSchema.Tool tool = McpSchema.Tool.builder()
-			.name("test-tool")
+		McpSchema.Tool tool = McpSchema.Tool.builder("test-tool", JSON_MAPPER, schemaJson)
 			.description("A test tool")
-			.inputSchema(JSON_MAPPER, schemaJson)
 			.build();
 
 		String value = JSON_MAPPER.writeValueAsString(tool);
@@ -831,10 +879,8 @@ public class McpSchemaTests {
 				}
 				""";
 
-		McpSchema.Tool tool = McpSchema.Tool.builder()
-			.name("addressTool")
+		McpSchema.Tool tool = McpSchema.Tool.builder("addressTool", JSON_MAPPER, complexSchemaJson)
 			.title("Handles addresses")
-			.inputSchema(JSON_MAPPER, complexSchemaJson)
 			.build();
 
 		// Serialize the tool to a string
@@ -877,11 +923,9 @@ public class McpSchemaTests {
 		Map<String, Object> inputSchema = Map.of("inputSchema", schemaJson);
 		Map<String, Object> meta = Map.of("metaKey", "metaValue");
 
-		McpSchema.Tool tool = McpSchema.Tool.builder()
-			.name("addressTool")
+		McpSchema.Tool tool = McpSchema.Tool.builder("addressTool", inputSchema)
 			.title("addressTool")
 			.description("Handles addresses")
-			.inputSchema(inputSchema)
 			.meta(meta)
 			.build();
 
@@ -906,13 +950,17 @@ public class McpSchemaTests {
 					"required": ["name"]
 				}
 				""";
-		McpSchema.ToolAnnotations annotations = new McpSchema.ToolAnnotations("A test tool", false, false, false, false,
-				false);
+		McpSchema.ToolAnnotations annotations = McpSchema.ToolAnnotations.builder()
+			.title("A test tool")
+			.readOnlyHint(false)
+			.destructiveHint(false)
+			.idempotentHint(false)
+			.openWorldHint(false)
+			.returnDirect(false)
+			.build();
 
-		McpSchema.Tool tool = McpSchema.Tool.builder()
-			.name("test-tool")
+		McpSchema.Tool tool = McpSchema.Tool.builder("test-tool", JSON_MAPPER, schemaJson)
 			.description("A test tool")
-			.inputSchema(JSON_MAPPER, schemaJson)
 			.annotations(annotations)
 			.build();
 
@@ -977,10 +1025,8 @@ public class McpSchemaTests {
 				}
 				""";
 
-		McpSchema.Tool tool = McpSchema.Tool.builder()
-			.name("test-tool")
+		McpSchema.Tool tool = McpSchema.Tool.builder("test-tool", JSON_MAPPER, inputSchemaJson)
 			.description("A test tool")
-			.inputSchema(JSON_MAPPER, inputSchemaJson)
 			.outputSchema(JSON_MAPPER, outputSchemaJson)
 			.build();
 
@@ -1041,13 +1087,17 @@ public class McpSchemaTests {
 				}
 				""";
 
-		McpSchema.ToolAnnotations annotations = new McpSchema.ToolAnnotations("A test tool with output", true, false,
-				true, false, true);
+		McpSchema.ToolAnnotations annotations = McpSchema.ToolAnnotations.builder()
+			.title("A test tool with output")
+			.readOnlyHint(true)
+			.destructiveHint(false)
+			.idempotentHint(true)
+			.openWorldHint(false)
+			.returnDirect(true)
+			.build();
 
-		McpSchema.Tool tool = McpSchema.Tool.builder()
-			.name("test-tool")
+		McpSchema.Tool tool = McpSchema.Tool.builder("test-tool", JSON_MAPPER, inputSchemaJson)
 			.description("A test tool")
-			.inputSchema(JSON_MAPPER, inputSchemaJson)
 			.outputSchema(JSON_MAPPER, outputSchemaJson)
 			.annotations(annotations)
 			.build();
@@ -1166,7 +1216,7 @@ public class McpSchemaTests {
 		arguments.put("name", "test");
 		arguments.put("value", 42);
 
-		McpSchema.CallToolRequest request = new McpSchema.CallToolRequest("test-tool", arguments);
+		McpSchema.CallToolRequest request = McpSchema.CallToolRequest.builder("test-tool").arguments(arguments).build();
 
 		String value = JSON_MAPPER.writeValueAsString(request);
 
@@ -1180,12 +1230,12 @@ public class McpSchemaTests {
 	@Test
 	void testCallToolRequestJsonArguments() throws Exception {
 
-		McpSchema.CallToolRequest request = new McpSchema.CallToolRequest(JSON_MAPPER, "test-tool", """
+		McpSchema.CallToolRequest request = McpSchema.CallToolRequest.builder("test-tool").arguments(JSON_MAPPER, """
 				{
 					"name": "test",
 					"value": 42
 				}
-				""");
+				""").build();
 
 		String value = JSON_MAPPER.writeValueAsString(request);
 
@@ -1261,7 +1311,7 @@ public class McpSchemaTests {
 
 	@Test
 	void testCallToolResult() throws Exception {
-		McpSchema.TextContent content = new McpSchema.TextContent("Tool execution result");
+		McpSchema.TextContent content = McpSchema.TextContent.builder("Tool execution result").build();
 
 		McpSchema.CallToolResult result = McpSchema.CallToolResult.builder()
 			.content(Collections.singletonList(content))
@@ -1294,8 +1344,8 @@ public class McpSchemaTests {
 
 	@Test
 	void testCallToolResultBuilderWithMultipleContents() throws Exception {
-		McpSchema.TextContent textContent = new McpSchema.TextContent("Text result");
-		McpSchema.ImageContent imageContent = new McpSchema.ImageContent(null, "base64data", "image/png");
+		McpSchema.TextContent textContent = McpSchema.TextContent.builder("Text result").build();
+		McpSchema.ImageContent imageContent = McpSchema.ImageContent.builder("base64data", "image/png").build();
 
 		McpSchema.CallToolResult result = McpSchema.CallToolResult.builder()
 			.addContent(textContent)
@@ -1315,8 +1365,8 @@ public class McpSchemaTests {
 
 	@Test
 	void testCallToolResultBuilderWithContentList() throws Exception {
-		McpSchema.TextContent textContent = new McpSchema.TextContent("Text result");
-		McpSchema.ImageContent imageContent = new McpSchema.ImageContent(null, "base64data", "image/png");
+		McpSchema.TextContent textContent = McpSchema.TextContent.builder("Text result").build();
+		McpSchema.ImageContent imageContent = McpSchema.ImageContent.builder("base64data", "image/png").build();
 		List<McpSchema.Content> contents = Arrays.asList(textContent, imageContent);
 
 		McpSchema.CallToolResult result = McpSchema.CallToolResult.builder().content(contents).isError(true).build();
@@ -1347,29 +1397,42 @@ public class McpSchemaTests {
 					{"content":[{"type":"text","text":"Error: Operation failed"}],"isError":true}"""));
 	}
 
+	@Test
+	void testCallToolResultDeserializationWithMissingContent() throws Exception {
+		McpSchema.CallToolResult result = JSON_MAPPER.readValue("""
+				{"isError":false}""", McpSchema.CallToolResult.class);
+
+		assertThat(result).isNotNull();
+		assertThat(result.content()).isEmpty();
+		assertThat(result.isError()).isFalse();
+	}
+
 	// Sampling Tests
 
 	@Test
 	void testCreateMessageRequest() throws Exception {
-		McpSchema.TextContent content = new McpSchema.TextContent("User message");
+		McpSchema.TextContent content = McpSchema.TextContent.builder("User message").build();
 
-		McpSchema.SamplingMessage message = new McpSchema.SamplingMessage(McpSchema.Role.USER, content);
+		McpSchema.SamplingMessage message = McpSchema.SamplingMessage.builder(McpSchema.Role.USER, content).build();
 
-		McpSchema.ModelHint hint = new McpSchema.ModelHint("gpt-4");
+		McpSchema.ModelHint hint = McpSchema.ModelHint.of("gpt-4");
 
-		McpSchema.ModelPreferences preferences = new McpSchema.ModelPreferences(Collections.singletonList(hint), 0.3,
-				0.7, 0.9);
+		McpSchema.ModelPreferences preferences = McpSchema.ModelPreferences.builder()
+			.hints(Collections.singletonList(hint))
+			.costPriority(0.3)
+			.speedPriority(0.7)
+			.intelligencePriority(0.9)
+			.build();
 
 		Map<String, Object> metadata = new HashMap<>();
 		metadata.put("session", "test-session");
 
-		McpSchema.CreateMessageRequest request = McpSchema.CreateMessageRequest.builder()
-			.messages(Collections.singletonList(message))
+		McpSchema.CreateMessageRequest request = McpSchema.CreateMessageRequest
+			.builder(Collections.singletonList(message), 1000)
 			.modelPreferences(preferences)
 			.systemPrompt("You are a helpful assistant")
 			.includeContext(McpSchema.CreateMessageRequest.ContextInclusionStrategy.THIS_SERVER)
 			.temperature(0.7)
-			.maxTokens(1000)
 			.stopSequences(Arrays.asList("STOP", "END"))
 			.metadata(metadata)
 			.build();
@@ -1385,13 +1448,31 @@ public class McpSchemaTests {
 	}
 
 	@Test
-	void testCreateMessageResult() throws Exception {
-		McpSchema.TextContent content = new McpSchema.TextContent("Assistant response");
+	void testSamplingMessageDeserializationWithMissingFields() throws Exception {
+		McpSchema.SamplingMessage message = JSON_MAPPER.readValue("{}", McpSchema.SamplingMessage.class);
 
-		McpSchema.CreateMessageResult result = McpSchema.CreateMessageResult.builder()
-			.role(McpSchema.Role.ASSISTANT)
-			.content(content)
-			.model("gpt-4")
+		assertThat(message).isNotNull();
+		assertThat(message.role()).isEqualTo(McpSchema.Role.USER);
+		assertThat(message.content()).isInstanceOf(McpSchema.TextContent.class);
+	}
+
+	@Test
+	void testCreateMessageRequestDeserializationWithMissingRequiredFields() throws Exception {
+		McpSchema.CreateMessageRequest request = JSON_MAPPER.readValue("""
+				{"systemPrompt":"hello"}""", McpSchema.CreateMessageRequest.class);
+
+		assertThat(request).isNotNull();
+		assertThat(request.messages()).isEmpty();
+		assertThat(request.maxTokens()).isZero();
+		assertThat(request.systemPrompt()).isEqualTo("hello");
+	}
+
+	@Test
+	void testCreateMessageResult() throws Exception {
+		McpSchema.TextContent content = McpSchema.TextContent.builder("Assistant response").build();
+
+		McpSchema.CreateMessageResult result = McpSchema.CreateMessageResult
+			.builder(McpSchema.Role.ASSISTANT, content, "gpt-4")
 			.stopReason(McpSchema.CreateMessageResult.StopReason.END_TURN)
 			.build();
 
@@ -1412,11 +1493,9 @@ public class McpSchemaTests {
 
 		McpSchema.CreateMessageResult value = JSON_MAPPER.readValue(input, McpSchema.CreateMessageResult.class);
 
-		McpSchema.TextContent expectedContent = new McpSchema.TextContent("Assistant response");
-		McpSchema.CreateMessageResult expected = McpSchema.CreateMessageResult.builder()
-			.role(McpSchema.Role.ASSISTANT)
-			.content(expectedContent)
-			.model("gpt-4")
+		McpSchema.TextContent expectedContent = McpSchema.TextContent.builder("Assistant response").build();
+		McpSchema.CreateMessageResult expected = McpSchema.CreateMessageResult
+			.builder(McpSchema.Role.ASSISTANT, expectedContent, "gpt-4")
 			.stopReason(McpSchema.CreateMessageResult.StopReason.UNKNOWN)
 			.build();
 		assertThat(value).isEqualTo(expected);
@@ -1426,9 +1505,9 @@ public class McpSchemaTests {
 
 	@Test
 	void testCreateElicitationRequest() throws Exception {
-		McpSchema.ElicitRequest request = McpSchema.ElicitRequest.builder()
-			.requestedSchema(Map.of("type", "object", "required", List.of("a"), "properties",
-					Map.of("foo", Map.of("type", "string"))))
+		McpSchema.ElicitRequest request = McpSchema.ElicitRequest
+			.builder("Please provide additional information", Map.of("type", "object", "required", List.of("a"),
+					"properties", Map.of("foo", Map.of("type", "string"))))
 			.build();
 
 		String value = JSON_MAPPER.writeValueAsString(request);
@@ -1436,15 +1515,15 @@ public class McpSchemaTests {
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
 			.when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
 			.isObject()
-			.isEqualTo(json("""
-					{"requestedSchema":{"properties":{"foo":{"type":"string"}},"required":["a"],"type":"object"}}"""));
+			.isEqualTo(
+					json("""
+							{"message":"Please provide additional information","requestedSchema":{"properties":{"foo":{"type":"string"}},"required":["a"],"type":"object"}}"""));
 	}
 
 	@Test
 	void testCreateElicitationResult() throws Exception {
-		McpSchema.ElicitResult result = McpSchema.ElicitResult.builder()
+		McpSchema.ElicitResult result = McpSchema.ElicitResult.builder(McpSchema.ElicitResult.Action.ACCEPT)
 			.content(Map.of("foo", "bar"))
-			.message(McpSchema.ElicitResult.Action.ACCEPT)
 			.build();
 
 		String value = JSON_MAPPER.writeValueAsString(result);
@@ -1456,6 +1535,15 @@ public class McpSchemaTests {
 					{"action":"accept","content":{"foo":"bar"}}"""));
 	}
 
+	@Test
+	void testElicitRequestDeserializationWithMissingRequiredFields() throws Exception {
+		McpSchema.ElicitRequest request = JSON_MAPPER.readValue("{}", McpSchema.ElicitRequest.class);
+
+		assertThat(request).isNotNull();
+		assertThat(request.message()).isEmpty();
+		assertThat(request.requestedSchema()).isEmpty();
+	}
+
 	@Test
 	void testElicitRequestWithMeta() throws Exception {
 		Map<String, Object> requestedSchema = Map.of("type", "object", "required", List.of("name"), "properties",
@@ -1464,9 +1552,7 @@ public class McpSchemaTests {
 		Map<String, Object> meta = new HashMap<>();
 		meta.put("progressToken", "elicit-token-789");
 
-		McpSchema.ElicitRequest request = McpSchema.ElicitRequest.builder()
-			.message("Please provide your name")
-			.requestedSchema(requestedSchema)
+		McpSchema.ElicitRequest request = McpSchema.ElicitRequest.builder("Please provide your name", requestedSchema)
 			.meta(meta)
 			.build();
 
@@ -1552,7 +1638,7 @@ public class McpSchemaTests {
 		McpSchema.CompleteRequest.CompleteArgument argument = new McpSchema.CompleteRequest.CompleteArgument("arg1",
 				"partial-value");
 
-		McpSchema.CompleteRequest request = new McpSchema.CompleteRequest(promptRef, argument);
+		McpSchema.CompleteRequest request = McpSchema.CompleteRequest.builder(promptRef, argument).build();
 
 		String value = JSON_MAPPER.writeValueAsString(request);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -1576,7 +1662,7 @@ public class McpSchemaTests {
 		Map<String, Object> meta = new HashMap<>();
 		meta.put("progressToken", "complete-progress-789");
 
-		McpSchema.CompleteRequest request = new McpSchema.CompleteRequest(resourceRef, argument, meta, null);
+		McpSchema.CompleteRequest request = McpSchema.CompleteRequest.builder(resourceRef, argument).meta(meta).build();
 
 		String value = JSON_MAPPER.writeValueAsString(request);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -1595,7 +1681,10 @@ public class McpSchemaTests {
 
 	@Test
 	void testRoot() throws Exception {
-		McpSchema.Root root = new McpSchema.Root("file:///path/to/root", "Test Root", Map.of("metaKey", "metaValue"));
+		McpSchema.Root root = McpSchema.Root.builder("file:///path/to/root")
+			.name("Test Root")
+			.meta(Map.of("metaKey", "metaValue"))
+			.build();
 
 		String value = JSON_MAPPER.writeValueAsString(root);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -1607,11 +1696,13 @@ public class McpSchemaTests {
 
 	@Test
 	void testListRootsResult() throws Exception {
-		McpSchema.Root root1 = new McpSchema.Root("file:///path/to/root1", "First Root");
+		McpSchema.Root root1 = McpSchema.Root.builder("file:///path/to/root1").name("First Root").build();
 
-		McpSchema.Root root2 = new McpSchema.Root("file:///path/to/root2", "Second Root");
+		McpSchema.Root root2 = McpSchema.Root.builder("file:///path/to/root2").name("Second Root").build();
 
-		McpSchema.ListRootsResult result = new McpSchema.ListRootsResult(Arrays.asList(root1, root2), "next-cursor");
+		McpSchema.ListRootsResult result = McpSchema.ListRootsResult.builder(Arrays.asList(root1, root2))
+			.nextCursor("next-cursor")
+			.build();
 
 		String value = JSON_MAPPER.writeValueAsString(result);
 
@@ -1729,8 +1820,11 @@ public class McpSchemaTests {
 
 	@Test
 	void testProgressNotificationWithMessage() throws Exception {
-		McpSchema.ProgressNotification notification = new McpSchema.ProgressNotification("progress-token-123", 0.5, 1.0,
-				"Processing file 1 of 2", Map.of("key", "value"));
+		McpSchema.ProgressNotification notification = McpSchema.ProgressNotification.builder("progress-token-123", 0.5)
+			.total(1.0)
+			.message("Processing file 1 of 2")
+			.meta(Map.of("key", "value"))
+			.build();
 
 		String value = JSON_MAPPER.writeValueAsString(notification);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -1755,10 +1849,21 @@ public class McpSchemaTests {
 		assertThat(notification.meta()).containsEntry("key", "value");
 	}
 
+	@Test
+	void testProgressNotificationDeserializationWithMissingRequiredFields() throws Exception {
+		McpSchema.ProgressNotification notification = JSON_MAPPER.readValue("""
+				{"total":1.0}""", McpSchema.ProgressNotification.class);
+
+		assertThat(notification).isNotNull();
+		assertThat(notification.progressToken()).isEqualTo("");
+		assertThat(notification.progress()).isZero();
+		assertThat(notification.total()).isEqualTo(1.0);
+	}
+
 	@Test
 	void testProgressNotificationWithoutMessage() throws Exception {
-		McpSchema.ProgressNotification notification = new McpSchema.ProgressNotification("progress-token-789", 0.25,
-				null, null);
+		McpSchema.ProgressNotification notification = McpSchema.ProgressNotification.builder("progress-token-789", 0.25)
+			.build();
 
 		String value = JSON_MAPPER.writeValueAsString(notification);
 		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
@@ -1768,4 +1873,15 @@ public class McpSchemaTests {
 					{"progressToken":"progress-token-789","progress":0.25}"""));
 	}
 
+	@Test
+	void testLoggingMessageNotificationDeserializationWithMissingRequiredFields() throws Exception {
+		McpSchema.LoggingMessageNotification notification = JSON_MAPPER.readValue("""
+				{"logger":"my-logger"}""", McpSchema.LoggingMessageNotification.class);
+
+		assertThat(notification).isNotNull();
+		assertThat(notification.level()).isEqualTo(McpSchema.LoggingLevel.INFO);
+		assertThat(notification.logger()).isEqualTo("my-logger");
+		assertThat(notification.data()).isEmpty();
+	}
+
 }