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>
2026-04-20 17:20:38 +02:00 · 2026-04-20 17:20:38 +02:00 · 22a0efa577
commit 22a0efa577
parent 599b43cac4
12 changed files with 4258 additions and 1688 deletions
--- a/mcp-core/src/test/java/io/modelcontextprotocol/client/LifecycleInitializerPostInitializationHookTests.java
+++ b/mcp-core/src/test/java/io/modelcontextprotocol/client/LifecycleInitializerPostInitializationHookTests.java
@ -43,13 +43,16 @@ class LifecycleInitializerPostInitializationHookTests {
 	private static final McpSchema.ClientCapabilities CLIENT_CAPABILITIES = McpSchema.ClientCapabilities.builder()
 		.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 final List<String> PROTOCOL_VERSIONS = List.of("1.0.0", "2.0.0");

-	private static final McpSchema.InitializeResult MOCK_INIT_RESULT = new McpSchema.InitializeResult("2.0.0",
-			McpSchema.ServerCapabilities.builder().build(), new McpSchema.Implementation("test-server", "1.0.0"),
-			"Test instructions");
+	private static final McpSchema.InitializeResult MOCK_INIT_RESULT = McpSchema.InitializeResult
+		.builder("2.0.0", McpSchema.ServerCapabilities.builder().build(),
+				McpSchema.Implementation.builder("test-server", "1.0.0").build())
+		.instructions("Test instructions")
+		.build();

 	@Mock
 	private McpClientSession mockClientSession;
--- a/mcp-core/src/test/java/io/modelcontextprotocol/client/LifecycleInitializerTests.java
+++ b/mcp-core/src/test/java/io/modelcontextprotocol/client/LifecycleInitializerTests.java
@ -44,13 +44,16 @@ class LifecycleInitializerTests {
 	private static final McpSchema.ClientCapabilities CLIENT_CAPABILITIES = McpSchema.ClientCapabilities.builder()
 		.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 final List<String> PROTOCOL_VERSIONS = List.of("1.0.0", "2.0.0");

-	private static final McpSchema.InitializeResult MOCK_INIT_RESULT = new McpSchema.InitializeResult("2.0.0",
-			McpSchema.ServerCapabilities.builder().build(), new McpSchema.Implementation("test-server", "1.0.0"),
-			"Test instructions");
+	private static final McpSchema.InitializeResult MOCK_INIT_RESULT = McpSchema.InitializeResult
+		.builder("2.0.0", McpSchema.ServerCapabilities.builder().build(),
+				McpSchema.Implementation.builder("test-server", "1.0.0").build())
+		.instructions("Test instructions")
+		.build();

 	@Mock
 	private McpClientSession mockClientSession;
@ -148,10 +151,12 @@ class LifecycleInitializerTests {

 	@Test
 	void shouldFailForUnsupportedProtocolVersion() {
-		McpSchema.InitializeResult unsupportedResult = new McpSchema.InitializeResult("999.0.0", // Unsupported
-																									// version
-				McpSchema.ServerCapabilities.builder().build(), new McpSchema.Implementation("test-server", "1.0.0"),
-				"Test instructions");
+		McpSchema.InitializeResult unsupportedResult = McpSchema.InitializeResult.builder("999.0.0", // Unsupported
+																										// version
+				McpSchema.ServerCapabilities.builder().build(),
+				McpSchema.Implementation.builder("test-server", "1.0.0").build())
+			.instructions("Test instructions")
+			.build();

 		when(mockClientSession.sendRequest(eq(McpSchema.METHOD_INITIALIZE), any(), any()))
 			.thenReturn(Mono.just(unsupportedResult));
@ -342,8 +347,11 @@ class LifecycleInitializerTests {

 		when(mockClientSession.sendRequest(eq(McpSchema.METHOD_INITIALIZE), any(), any())).thenAnswer(invocation -> {
 			capturedRequest.set((McpSchema.InitializeRequest) invocation.getArgument(1));
-			return Mono.just(new McpSchema.InitializeResult("4.0.0", McpSchema.ServerCapabilities.builder().build(),
-					new McpSchema.Implementation("test-server", "1.0.0"), "Test instructions"));
+			return Mono.just(McpSchema.InitializeResult
+				.builder("4.0.0", McpSchema.ServerCapabilities.builder().build(),
+						McpSchema.Implementation.builder("test-server", "1.0.0").build())
+				.instructions("Test instructions")
+				.build());
 		});

 		StepVerifier.create(initializer.withInitialization("test", init -> Mono.just(init.initializeResult())))
--- a/mcp-core/src/test/java/io/modelcontextprotocol/server/AsyncToolSpecificationBuilderTest.java
+++ b/mcp-core/src/test/java/io/modelcontextprotocol/server/AsyncToolSpecificationBuilderTest.java
@ -42,16 +42,15 @@ class AsyncToolSpecificationBuilderTest {
 	@Test
 	void builderShouldCreateValidAsyncToolSpecification() {

-		Tool tool = McpSchema.Tool.builder()
-			.name("test-tool")
-			.title("A test tool")
-			.inputSchema(EMPTY_JSON_SCHEMA)
-			.build();
+		Tool tool = McpSchema.Tool.builder("test-tool", EMPTY_JSON_SCHEMA).title("A test tool").build();

 		McpServerFeatures.AsyncToolSpecification specification = McpServerFeatures.AsyncToolSpecification.builder()
 			.tool(tool)
-			.callHandler((exchange, request) -> Mono
-				.just(CallToolResult.builder().content(List.of(new TextContent("Test result"))).isError(false).build()))
+			.callHandler((exchange,
+					request) -> Mono.just(CallToolResult.builder()
+						.content(List.of(TextContent.builder("Test result").build()))
+						.isError(false)
+						.build()))
 			.build();

 		assertThat(specification).isNotNull();
@ -69,11 +68,7 @@ class AsyncToolSpecificationBuilderTest {

 	@Test
 	void builderShouldThrowExceptionWhenCallToolIsNull() {
-		Tool tool = McpSchema.Tool.builder()
-			.name("test-tool")
-			.title("A test tool")
-			.inputSchema(EMPTY_JSON_SCHEMA)
-			.build();
+		Tool tool = McpSchema.Tool.builder("test-tool", EMPTY_JSON_SCHEMA).title("A test tool").build();

 		assertThatThrownBy(() -> McpServerFeatures.AsyncToolSpecification.builder().tool(tool).build())
 			.isInstanceOf(IllegalArgumentException.class)
@ -82,11 +77,7 @@ class AsyncToolSpecificationBuilderTest {

 	@Test
 	void builderShouldAllowMethodChaining() {
-		Tool tool = McpSchema.Tool.builder()
-			.name("test-tool")
-			.title("A test tool")
-			.inputSchema(EMPTY_JSON_SCHEMA)
-			.build();
+		Tool tool = McpSchema.Tool.builder("test-tool", EMPTY_JSON_SCHEMA).title("A test tool").build();
 		McpServerFeatures.AsyncToolSpecification.Builder builder = McpServerFeatures.AsyncToolSpecification.builder();

 		// Then - verify method chaining returns the same builder instance
@ -98,20 +89,19 @@ class AsyncToolSpecificationBuilderTest {

 	@Test
 	void builtSpecificationShouldExecuteCallToolCorrectly() {
-		Tool tool = McpSchema.Tool.builder()
-			.name("calculator")
-			.title("Simple calculator")
-			.inputSchema(EMPTY_JSON_SCHEMA)
-			.build();
+		Tool tool = McpSchema.Tool.builder("calculator", EMPTY_JSON_SCHEMA).title("Simple calculator").build();
 		String expectedResult = "42";

 		McpServerFeatures.AsyncToolSpecification specification = McpServerFeatures.AsyncToolSpecification.builder()
 			.tool(tool)
-			.callHandler((exchange, request) -> Mono.just(
-					CallToolResult.builder().content(List.of(new TextContent(expectedResult))).isError(false).build()))
+			.callHandler((exchange,
+					request) -> Mono.just(CallToolResult.builder()
+						.content(List.of(TextContent.builder(expectedResult).build()))
+						.isError(false)
+						.build()))
 			.build();

-		CallToolRequest request = new CallToolRequest("calculator", Map.of());
+		CallToolRequest request = CallToolRequest.builder("calculator").build();
 		Mono<CallToolResult> resultMono = specification.callHandler().apply(null, request);

 		StepVerifier.create(resultMono).assertNext(result -> {
@ -125,18 +115,14 @@ class AsyncToolSpecificationBuilderTest {

 	@Test
 	void fromSyncShouldConvertSyncToolSpecificationCorrectly() {
-		Tool tool = McpSchema.Tool.builder()
-			.name("sync-tool")
-			.title("A sync tool")
-			.inputSchema(EMPTY_JSON_SCHEMA)
-			.build();
+		Tool tool = McpSchema.Tool.builder("sync-tool", EMPTY_JSON_SCHEMA).title("A sync tool").build();
 		String expectedResult = "sync result";

 		// Create a sync tool specification
 		McpServerFeatures.SyncToolSpecification syncSpec = McpServerFeatures.SyncToolSpecification.builder()
 			.tool(tool)
 			.callHandler((exchange, request) -> CallToolResult.builder()
-				.content(List.of(new TextContent(expectedResult)))
+				.content(List.of(TextContent.builder(expectedResult).build()))
 				.isError(false)
 				.build())
 			.build();
@ -150,7 +136,7 @@ class AsyncToolSpecificationBuilderTest {
 		assertThat(asyncSpec.callHandler()).isNotNull();

 		// Test that the converted async specification works correctly
-		CallToolRequest request = new CallToolRequest("sync-tool", Map.of("param", "value"));
+		CallToolRequest request = CallToolRequest.builder("sync-tool").arguments(Map.of("param", "value")).build();
 		Mono<CallToolResult> resultMono = asyncSpec.callHandler().apply(null, request);

 		StepVerifier.create(resultMono).assertNext(result -> {
@ -193,7 +179,7 @@ class AsyncToolSpecificationBuilderTest {

 		@Test
 		void defaultShouldThrowOnInvalidName() {
-			Tool invalidTool = Tool.builder().name("invalid tool name").build();
+			Tool invalidTool = Tool.builder("invalid tool name", EMPTY_JSON_SCHEMA).build();

 			assertThatThrownBy(
 					() -> McpServer.async(transportProvider).toolCall(invalidTool, (exchange, request) -> null))
@ -204,7 +190,7 @@ class AsyncToolSpecificationBuilderTest {
 		@Test
 		void lenientDefaultShouldLogOnInvalidName() {
 			System.setProperty(ToolNameValidator.STRICT_VALIDATION_PROPERTY, "false");
-			Tool invalidTool = Tool.builder().name("invalid tool name").build();
+			Tool invalidTool = Tool.builder("invalid tool name", EMPTY_JSON_SCHEMA).build();

 			assertThatCode(() -> McpServer.async(transportProvider).toolCall(invalidTool, (exchange, request) -> null))
 				.doesNotThrowAnyException();
@ -213,7 +199,7 @@ class AsyncToolSpecificationBuilderTest {

 		@Test
 		void lenientConfigurationShouldLogOnInvalidName() {
-			Tool invalidTool = Tool.builder().name("invalid tool name").build();
+			Tool invalidTool = Tool.builder("invalid tool name", EMPTY_JSON_SCHEMA).build();

 			assertThatCode(() -> McpServer.async(transportProvider)
 				.strictToolNameValidation(false)
@ -224,7 +210,7 @@ class AsyncToolSpecificationBuilderTest {
 		@Test
 		void serverConfigurationShouldOverrideDefault() {
 			System.setProperty(ToolNameValidator.STRICT_VALIDATION_PROPERTY, "false");
-			Tool invalidTool = Tool.builder().name("invalid tool name").build();
+			Tool invalidTool = Tool.builder("invalid tool name", EMPTY_JSON_SCHEMA).build();

 			assertThatThrownBy(() -> McpServer.async(transportProvider)
 				.strictToolNameValidation(true)
--- a/mcp-core/src/test/java/io/modelcontextprotocol/server/McpAsyncServerExchangeTests.java
+++ b/mcp-core/src/test/java/io/modelcontextprotocol/server/McpAsyncServerExchangeTests.java
@ -52,7 +52,7 @@ class McpAsyncServerExchangeTests {

 		clientCapabilities = McpSchema.ClientCapabilities.builder().roots(true).build();

-		clientInfo = new McpSchema.Implementation("test-client", "1.0.0");
+		clientInfo = McpSchema.Implementation.builder("test-client", "1.0.0").build();

 		exchange = new McpAsyncServerExchange("testSessionId", mockSession, clientCapabilities, clientInfo,
 				McpTransportContext.EMPTY);
@ -61,9 +61,10 @@ class McpAsyncServerExchangeTests {
 	@Test
 	void testListRootsWithSinglePage() {

-		List<McpSchema.Root> roots = Arrays.asList(new McpSchema.Root("file:///home/user/project1", "Project 1"),
-				new McpSchema.Root("file:///home/user/project2", "Project 2"));
-		McpSchema.ListRootsResult singlePageResult = new McpSchema.ListRootsResult(roots, null);
+		List<McpSchema.Root> roots = Arrays.asList(
+				McpSchema.Root.builder("file:///home/user/project1").name("Project 1").build(),
+				McpSchema.Root.builder("file:///home/user/project2").name("Project 2").build());
+		McpSchema.ListRootsResult singlePageResult = McpSchema.ListRootsResult.builder(roots).build();

 		when(mockSession.sendRequest(eq(McpSchema.METHOD_ROOTS_LIST), any(McpSchema.PaginatedRequest.class),
 				any(TypeRef.class)))
@ -78,7 +79,7 @@ class McpAsyncServerExchangeTests {
 			assertThat(result.nextCursor()).isNull();

 			// Verify that the returned list is unmodifiable
-			assertThatThrownBy(() -> result.roots().add(new McpSchema.Root("file:///test", "Test")))
+			assertThatThrownBy(() -> result.roots().add(McpSchema.Root.builder("file:///test").name("Test").build()))
 				.isInstanceOf(UnsupportedOperationException.class);
 		}).verifyComplete();
 	}
@ -86,14 +87,18 @@ class McpAsyncServerExchangeTests {
 	@Test
 	void testListRootsWithMultiplePages() {

-		List<McpSchema.Root> page1Roots = Arrays.asList(new McpSchema.Root("file:///home/user/project1", "Project 1"),
-				new McpSchema.Root("file:///home/user/project2", "Project 2"));
-		List<McpSchema.Root> page2Roots = Arrays.asList(new McpSchema.Root("file:///home/user/project3", "Project 3"));
+		List<McpSchema.Root> page1Roots = Arrays.asList(
+				McpSchema.Root.builder("file:///home/user/project1").name("Project 1").build(),
+				McpSchema.Root.builder("file:///home/user/project2").name("Project 2").build());
+		List<McpSchema.Root> page2Roots = Arrays
+			.asList(McpSchema.Root.builder("file:///home/user/project3").name("Project 3").build());

-		McpSchema.ListRootsResult page1Result = new McpSchema.ListRootsResult(page1Roots, "cursor1");
-		McpSchema.ListRootsResult page2Result = new McpSchema.ListRootsResult(page2Roots, null);
+		McpSchema.ListRootsResult page1Result = McpSchema.ListRootsResult.builder(page1Roots)
+			.nextCursor("cursor1")
+			.build();
+		McpSchema.ListRootsResult page2Result = McpSchema.ListRootsResult.builder(page2Roots).build();

-		when(mockSession.sendRequest(eq(McpSchema.METHOD_ROOTS_LIST), eq(new McpSchema.PaginatedRequest(null)),
+		when(mockSession.sendRequest(eq(McpSchema.METHOD_ROOTS_LIST), eq(new McpSchema.PaginatedRequest()),
 				any(TypeRef.class)))
 			.thenReturn(Mono.just(page1Result));

@ -109,7 +114,7 @@ class McpAsyncServerExchangeTests {
 			assertThat(result.nextCursor()).isNull();

 			// Verify that the returned list is unmodifiable
-			assertThatThrownBy(() -> result.roots().add(new McpSchema.Root("file:///test", "Test")))
+			assertThatThrownBy(() -> result.roots().add(McpSchema.Root.builder("file:///test").name("Test").build()))
 				.isInstanceOf(UnsupportedOperationException.class);
 		}).verifyComplete();
 	}
@ -117,7 +122,7 @@ class McpAsyncServerExchangeTests {
 	@Test
 	void testListRootsWithEmptyResult() {

-		McpSchema.ListRootsResult emptyResult = new McpSchema.ListRootsResult(new ArrayList<>(), null);
+		McpSchema.ListRootsResult emptyResult = McpSchema.ListRootsResult.builder(new ArrayList<>()).build();

 		when(mockSession.sendRequest(eq(McpSchema.METHOD_ROOTS_LIST), any(McpSchema.PaginatedRequest.class),
 				any(TypeRef.class)))
@ -128,7 +133,7 @@ class McpAsyncServerExchangeTests {
 			assertThat(result.nextCursor()).isNull();

 			// Verify that the returned list is unmodifiable
-			assertThatThrownBy(() -> result.roots().add(new McpSchema.Root("file:///test", "Test")))
+			assertThatThrownBy(() -> result.roots().add(McpSchema.Root.builder("file:///test").name("Test").build()))
 				.isInstanceOf(UnsupportedOperationException.class);
 		}).verifyComplete();
 	}
@ -136,8 +141,9 @@ class McpAsyncServerExchangeTests {
 	@Test
 	void testListRootsWithSpecificCursor() {

-		List<McpSchema.Root> roots = Arrays.asList(new McpSchema.Root("file:///home/user/project3", "Project 3"));
-		McpSchema.ListRootsResult result = new McpSchema.ListRootsResult(roots, "nextCursor");
+		List<McpSchema.Root> roots = Arrays
+			.asList(McpSchema.Root.builder("file:///home/user/project3").name("Project 3").build());
+		McpSchema.ListRootsResult result = McpSchema.ListRootsResult.builder(roots).nextCursor("nextCursor").build();

 		when(mockSession.sendRequest(eq(McpSchema.METHOD_ROOTS_LIST), eq(new McpSchema.PaginatedRequest("someCursor")),
 				any(TypeRef.class)))
@ -167,12 +173,14 @@ class McpAsyncServerExchangeTests {
 	void testListRootsUnmodifiabilityAfterAccumulation() {

 		List<McpSchema.Root> page1Roots = new ArrayList<>(
-				Arrays.asList(new McpSchema.Root("file:///home/user/project1", "Project 1")));
+				Arrays.asList(McpSchema.Root.builder("file:///home/user/project1").name("Project 1").build()));
 		List<McpSchema.Root> page2Roots = new ArrayList<>(
-				Arrays.asList(new McpSchema.Root("file:///home/user/project2", "Project 2")));
+				Arrays.asList(McpSchema.Root.builder("file:///home/user/project2").name("Project 2").build()));

-		McpSchema.ListRootsResult page1Result = new McpSchema.ListRootsResult(page1Roots, "cursor1");
-		McpSchema.ListRootsResult page2Result = new McpSchema.ListRootsResult(page2Roots, null);
+		McpSchema.ListRootsResult page1Result = McpSchema.ListRootsResult.builder(page1Roots)
+			.nextCursor("cursor1")
+			.build();
+		McpSchema.ListRootsResult page2Result = McpSchema.ListRootsResult.builder(page2Roots).build();

 		when(mockSession.sendRequest(eq(McpSchema.METHOD_ROOTS_LIST), eq(new McpSchema.PaginatedRequest(null)),
 				any(TypeRef.class)))
@ -187,7 +195,7 @@ class McpAsyncServerExchangeTests {
 			assertThat(result.roots()).hasSize(2);

 			// Verify that the returned list is unmodifiable
-			assertThatThrownBy(() -> result.roots().add(new McpSchema.Root("file:///test", "Test")))
+			assertThatThrownBy(() -> result.roots().add(McpSchema.Root.builder("file:///test").name("Test").build()))
 				.isInstanceOf(UnsupportedOperationException.class);

 			// Verify that clear() also throws UnsupportedOperationException
@ -227,10 +235,9 @@ class McpAsyncServerExchangeTests {

 	@Test
 	void testLoggingNotificationWithAllowedLevel() {
-		McpSchema.LoggingMessageNotification notification = McpSchema.LoggingMessageNotification.builder()
-			.level(McpSchema.LoggingLevel.ERROR)
+		McpSchema.LoggingMessageNotification notification = McpSchema.LoggingMessageNotification
+			.builder(McpSchema.LoggingLevel.ERROR, "Test error message")
 			.logger("test-logger")
-			.data("Test error message")
 			.build();

 		when(mockSession.isNotificationForLevelAllowed(any())).thenReturn(Boolean.TRUE);
@ -248,10 +255,9 @@ class McpAsyncServerExchangeTests {
 		exchange.setMinLoggingLevel(McpSchema.LoggingLevel.DEBUG);
 		verify(mockSession, times(1)).setMinLoggingLevel(eq(McpSchema.LoggingLevel.DEBUG));

-		McpSchema.LoggingMessageNotification debugNotification = McpSchema.LoggingMessageNotification.builder()
-			.level(McpSchema.LoggingLevel.DEBUG)
+		McpSchema.LoggingMessageNotification debugNotification = McpSchema.LoggingMessageNotification
+			.builder(McpSchema.LoggingLevel.DEBUG, "Debug message that should be filtered")
 			.logger("test-logger")
-			.data("Debug message that should be filtered")
 			.build();

 		when(mockSession.isNotificationForLevelAllowed(eq(McpSchema.LoggingLevel.DEBUG))).thenReturn(Boolean.TRUE);
@ -264,10 +270,9 @@ class McpAsyncServerExchangeTests {
 		verify(mockSession, times(1)).sendNotification(eq(McpSchema.METHOD_NOTIFICATION_MESSAGE),
 				eq(debugNotification));

-		McpSchema.LoggingMessageNotification warningNotification = McpSchema.LoggingMessageNotification.builder()
-			.level(McpSchema.LoggingLevel.WARNING)
+		McpSchema.LoggingMessageNotification warningNotification = McpSchema.LoggingMessageNotification
+			.builder(McpSchema.LoggingLevel.WARNING, "Debug message that should be filtered")
 			.logger("test-logger")
-			.data("Debug message that should be filtered")
 			.build();

 		StepVerifier.create(exchange.loggingNotification(warningNotification)).verifyComplete();
@ -279,10 +284,9 @@ class McpAsyncServerExchangeTests {

 	@Test
 	void testLoggingNotificationWithSessionError() {
-		McpSchema.LoggingMessageNotification notification = McpSchema.LoggingMessageNotification.builder()
-			.level(McpSchema.LoggingLevel.ERROR)
+		McpSchema.LoggingMessageNotification notification = McpSchema.LoggingMessageNotification
+			.builder(McpSchema.LoggingLevel.ERROR, "Test error message")
 			.logger("test-logger")
-			.data("Test error message")
 			.build();

 		when(mockSession.isNotificationForLevelAllowed(any())).thenReturn(Boolean.TRUE);
@ -304,8 +308,8 @@ class McpAsyncServerExchangeTests {
 		McpAsyncServerExchange exchangeWithNullCapabilities = new McpAsyncServerExchange("testSessionId", mockSession,
 				null, clientInfo, McpTransportContext.EMPTY);

-		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest.builder()
-			.message("Please provide your name")
+		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest
+			.builder("Please provide your name", Map.of("type", "object"))
 			.build();

 		StepVerifier.create(exchangeWithNullCapabilities.createElicitation(elicitRequest))
@ -328,8 +332,8 @@ class McpAsyncServerExchangeTests {
 		McpAsyncServerExchange exchangeWithoutElicitation = new McpAsyncServerExchange("testSessionId", mockSession,
 				capabilitiesWithoutElicitation, clientInfo, McpTransportContext.EMPTY);

-		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest.builder()
-			.message("Please provide your name")
+		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest
+			.builder("Please provide your name", Map.of("type", "object"))
 			.build();

 		StepVerifier.create(exchangeWithoutElicitation.createElicitation(elicitRequest)).verifyErrorSatisfies(error -> {
@ -359,17 +363,15 @@ class McpAsyncServerExchangeTests {
 				java.util.Map.of("type", "number")));
 		requestedSchema.put("required", java.util.List.of("name"));

-		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest.builder()
-			.message("Please provide your personal information")
-			.requestedSchema(requestedSchema)
+		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest
+			.builder("Please provide your personal information", requestedSchema)
 			.build();

 		java.util.Map<String, Object> responseContent = new java.util.HashMap<>();
 		responseContent.put("name", "John Doe");
 		responseContent.put("age", 30);

-		McpSchema.ElicitResult expectedResult = McpSchema.ElicitResult.builder()
-			.message(McpSchema.ElicitResult.Action.ACCEPT)
+		McpSchema.ElicitResult expectedResult = McpSchema.ElicitResult.builder(McpSchema.ElicitResult.Action.ACCEPT)
 			.content(responseContent)
 			.build();

@ -395,12 +397,11 @@ class McpAsyncServerExchangeTests {
 		McpAsyncServerExchange exchangeWithElicitation = new McpAsyncServerExchange("testSessionId", mockSession,
 				capabilitiesWithElicitation, clientInfo, McpTransportContext.EMPTY);

-		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest.builder()
-			.message("Please provide sensitive information")
+		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest
+			.builder("Please provide sensitive information", Map.of("type", "object"))
 			.build();

-		McpSchema.ElicitResult expectedResult = McpSchema.ElicitResult.builder()
-			.message(McpSchema.ElicitResult.Action.DECLINE)
+		McpSchema.ElicitResult expectedResult = McpSchema.ElicitResult.builder(McpSchema.ElicitResult.Action.DECLINE)
 			.build();

 		when(mockSession.sendRequest(eq(McpSchema.METHOD_ELICITATION_CREATE), eq(elicitRequest), any(TypeRef.class)))
@ -422,12 +423,11 @@ class McpAsyncServerExchangeTests {
 		McpAsyncServerExchange exchangeWithElicitation = new McpAsyncServerExchange("testSessionId", mockSession,
 				capabilitiesWithElicitation, clientInfo, McpTransportContext.EMPTY);

-		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest.builder()
-			.message("Please provide your information")
+		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest
+			.builder("Please provide your information", Map.of("type", "object"))
 			.build();

-		McpSchema.ElicitResult expectedResult = McpSchema.ElicitResult.builder()
-			.message(McpSchema.ElicitResult.Action.CANCEL)
+		McpSchema.ElicitResult expectedResult = McpSchema.ElicitResult.builder(McpSchema.ElicitResult.Action.CANCEL)
 			.build();

 		when(mockSession.sendRequest(eq(McpSchema.METHOD_ELICITATION_CREATE), eq(elicitRequest), any(TypeRef.class)))
@ -449,8 +449,8 @@ class McpAsyncServerExchangeTests {
 		McpAsyncServerExchange exchangeWithElicitation = new McpAsyncServerExchange("testSessionId", mockSession,
 				capabilitiesWithElicitation, clientInfo, McpTransportContext.EMPTY);

-		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest.builder()
-			.message("Please provide your name")
+		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest
+			.builder("Please provide your name", Map.of("type", "object"))
 			.build();

 		when(mockSession.sendRequest(eq(McpSchema.METHOD_ELICITATION_CREATE), eq(elicitRequest), any(TypeRef.class)))
@ -471,9 +471,10 @@ class McpAsyncServerExchangeTests {
 		McpAsyncServerExchange exchangeWithNullCapabilities = new McpAsyncServerExchange("testSessionId", mockSession,
 				null, clientInfo, McpTransportContext.EMPTY);

-		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest.builder()
-			.messages(Arrays
-				.asList(new McpSchema.SamplingMessage(McpSchema.Role.USER, new McpSchema.TextContent("Hello, world!"))))
+		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest
+			.builder(Arrays.asList(McpSchema.SamplingMessage
+				.builder(McpSchema.Role.USER, McpSchema.TextContent.builder("Hello, world!").build())
+				.build()), 1000)
 			.build();

 		StepVerifier.create(exchangeWithNullCapabilities.createMessage(createMessageRequest))
@ -497,9 +498,10 @@ class McpAsyncServerExchangeTests {
 		McpAsyncServerExchange exchangeWithoutSampling = new McpAsyncServerExchange("testSessionId", mockSession,
 				capabilitiesWithoutSampling, clientInfo, McpTransportContext.EMPTY);

-		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest.builder()
-			.messages(Arrays
-				.asList(new McpSchema.SamplingMessage(McpSchema.Role.USER, new McpSchema.TextContent("Hello, world!"))))
+		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest
+			.builder(Arrays.asList(McpSchema.SamplingMessage
+				.builder(McpSchema.Role.USER, McpSchema.TextContent.builder("Hello, world!").build())
+				.build()), 1000)
 			.build();

 		StepVerifier.create(exchangeWithoutSampling.createMessage(createMessageRequest)).verifyErrorSatisfies(error -> {
@ -522,15 +524,15 @@ class McpAsyncServerExchangeTests {
 		McpAsyncServerExchange exchangeWithSampling = new McpAsyncServerExchange("testSessionId", mockSession,
 				capabilitiesWithSampling, clientInfo, McpTransportContext.EMPTY);

-		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest.builder()
-			.messages(Arrays
-				.asList(new McpSchema.SamplingMessage(McpSchema.Role.USER, new McpSchema.TextContent("Hello, world!"))))
+		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest
+			.builder(Arrays.asList(McpSchema.SamplingMessage
+				.builder(McpSchema.Role.USER, McpSchema.TextContent.builder("Hello, world!").build())
+				.build()), 1000)
 			.build();

-		McpSchema.CreateMessageResult expectedResult = McpSchema.CreateMessageResult.builder()
-			.role(McpSchema.Role.ASSISTANT)
-			.content(new McpSchema.TextContent("Hello! How can I help you today?"))
-			.model("gpt-4")
+		McpSchema.CreateMessageResult expectedResult = McpSchema.CreateMessageResult
+			.builder(McpSchema.Role.ASSISTANT,
+					McpSchema.TextContent.builder("Hello! How can I help you today?").build(), "gpt-4")
 			.stopReason(McpSchema.CreateMessageResult.StopReason.END_TURN)
 			.build();

@ -559,16 +561,20 @@ class McpAsyncServerExchangeTests {
 				capabilitiesWithSampling, clientInfo, McpTransportContext.EMPTY);

 		// Create request with image content
-		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest.builder()
-			.messages(Arrays.asList(new McpSchema.SamplingMessage(McpSchema.Role.USER,
-					new McpSchema.ImageContent(null, "data:image/jpeg;base64,/9j/4AAQSkZJRgABAQEAYABgAAD...",
-							"image/jpeg"))))
+		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest.builder(Arrays.asList(
+				McpSchema.SamplingMessage
+					.builder(McpSchema.Role.USER,
+							McpSchema.ImageContent
+								.builder("data:image/jpeg;base64,/9j/4AAQSkZJRgABAQEAYABgAAD...", "image/jpeg")
+								.build())
+					.build()),
+				1000)
 			.build();

-		McpSchema.CreateMessageResult expectedResult = McpSchema.CreateMessageResult.builder()
-			.role(McpSchema.Role.ASSISTANT)
-			.content(new McpSchema.TextContent("I can see an image. It appears to be a photograph."))
-			.model("gpt-4-vision")
+		McpSchema.CreateMessageResult expectedResult = McpSchema.CreateMessageResult
+			.builder(McpSchema.Role.ASSISTANT,
+					McpSchema.TextContent.builder("I can see an image. It appears to be a photograph.").build(),
+					"gpt-4-vision")
 			.stopReason(McpSchema.CreateMessageResult.StopReason.END_TURN)
 			.build();

@ -593,9 +599,10 @@ class McpAsyncServerExchangeTests {
 		McpAsyncServerExchange exchangeWithSampling = new McpAsyncServerExchange("testSessionId", mockSession,
 				capabilitiesWithSampling, clientInfo, McpTransportContext.EMPTY);

-		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest.builder()
-			.messages(Arrays
-				.asList(new McpSchema.SamplingMessage(McpSchema.Role.USER, new McpSchema.TextContent("Hello"))))
+		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest.builder(Arrays.asList(
+				McpSchema.SamplingMessage.builder(McpSchema.Role.USER, McpSchema.TextContent.builder("Hello").build())
+					.build()),
+				1000)
 			.build();

 		when(mockSession.sendRequest(eq(McpSchema.METHOD_SAMPLING_CREATE_MESSAGE), eq(createMessageRequest),
@ -617,16 +624,17 @@ class McpAsyncServerExchangeTests {
 		McpAsyncServerExchange exchangeWithSampling = new McpAsyncServerExchange("testSessionId", mockSession,
 				capabilitiesWithSampling, clientInfo, McpTransportContext.EMPTY);

-		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest.builder()
-			.messages(Arrays.asList(new McpSchema.SamplingMessage(McpSchema.Role.USER,
-					new McpSchema.TextContent("What files are available?"))))
+		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest
+			.builder(Arrays.asList(McpSchema.SamplingMessage
+				.builder(McpSchema.Role.USER, McpSchema.TextContent.builder("What files are available?").build())
+				.build()), 1000)
 			.includeContext(McpSchema.CreateMessageRequest.ContextInclusionStrategy.ALL_SERVERS)
 			.build();

-		McpSchema.CreateMessageResult expectedResult = McpSchema.CreateMessageResult.builder()
-			.role(McpSchema.Role.ASSISTANT)
-			.content(new McpSchema.TextContent("Based on the available context, I can see several files..."))
-			.model("gpt-4")
+		McpSchema.CreateMessageResult expectedResult = McpSchema.CreateMessageResult
+			.builder(McpSchema.Role.ASSISTANT,
+					McpSchema.TextContent.builder("Based on the available context, I can see several files...").build(),
+					"gpt-4")
 			.stopReason(McpSchema.CreateMessageResult.StopReason.END_TURN)
 			.build();

--- a/mcp-core/src/test/java/io/modelcontextprotocol/server/McpSyncServerExchangeTests.java
+++ b/mcp-core/src/test/java/io/modelcontextprotocol/server/McpSyncServerExchangeTests.java
@ -53,7 +53,7 @@ class McpSyncServerExchangeTests {

 		clientCapabilities = McpSchema.ClientCapabilities.builder().roots(true).build();

-		clientInfo = new McpSchema.Implementation("test-client", "1.0.0");
+		clientInfo = McpSchema.Implementation.builder("test-client", "1.0.0").build();

 		asyncExchange = new McpAsyncServerExchange("testSessionId", mockSession, clientCapabilities, clientInfo,
 				McpTransportContext.EMPTY);
@ -63,9 +63,10 @@ class McpSyncServerExchangeTests {
 	@Test
 	void testListRootsWithSinglePage() {

-		List<McpSchema.Root> roots = Arrays.asList(new McpSchema.Root("file:///home/user/project1", "Project 1"),
-				new McpSchema.Root("file:///home/user/project2", "Project 2"));
-		McpSchema.ListRootsResult singlePageResult = new McpSchema.ListRootsResult(roots, null);
+		List<McpSchema.Root> roots = Arrays.asList(
+				McpSchema.Root.builder("file:///home/user/project1").name("Project 1").build(),
+				McpSchema.Root.builder("file:///home/user/project2").name("Project 2").build());
+		McpSchema.ListRootsResult singlePageResult = McpSchema.ListRootsResult.builder(roots).build();

 		when(mockSession.sendRequest(eq(McpSchema.METHOD_ROOTS_LIST), any(McpSchema.PaginatedRequest.class),
 				any(TypeRef.class)))
@ -81,19 +82,23 @@ class McpSyncServerExchangeTests {
 		assertThat(result.nextCursor()).isNull();

 		// Verify that the returned list is unmodifiable
-		assertThatThrownBy(() -> result.roots().add(new McpSchema.Root("file:///test", "Test")))
+		assertThatThrownBy(() -> result.roots().add(McpSchema.Root.builder("file:///test").name("Test").build()))
 			.isInstanceOf(UnsupportedOperationException.class);
 	}

 	@Test
 	void testListRootsWithMultiplePages() {

-		List<McpSchema.Root> page1Roots = Arrays.asList(new McpSchema.Root("file:///home/user/project1", "Project 1"),
-				new McpSchema.Root("file:///home/user/project2", "Project 2"));
-		List<McpSchema.Root> page2Roots = Arrays.asList(new McpSchema.Root("file:///home/user/project3", "Project 3"));
+		List<McpSchema.Root> page1Roots = Arrays.asList(
+				McpSchema.Root.builder("file:///home/user/project1").name("Project 1").build(),
+				McpSchema.Root.builder("file:///home/user/project2").name("Project 2").build());
+		List<McpSchema.Root> page2Roots = Arrays
+			.asList(McpSchema.Root.builder("file:///home/user/project3").name("Project 3").build());

-		McpSchema.ListRootsResult page1Result = new McpSchema.ListRootsResult(page1Roots, "cursor1");
-		McpSchema.ListRootsResult page2Result = new McpSchema.ListRootsResult(page2Roots, null);
+		McpSchema.ListRootsResult page1Result = McpSchema.ListRootsResult.builder(page1Roots)
+			.nextCursor("cursor1")
+			.build();
+		McpSchema.ListRootsResult page2Result = McpSchema.ListRootsResult.builder(page2Roots).build();

 		when(mockSession.sendRequest(eq(McpSchema.METHOD_ROOTS_LIST), eq(new McpSchema.PaginatedRequest(null)),
 				any(TypeRef.class)))
@ -112,14 +117,14 @@ class McpSyncServerExchangeTests {
 		assertThat(result.nextCursor()).isNull();

 		// Verify that the returned list is unmodifiable
-		assertThatThrownBy(() -> result.roots().add(new McpSchema.Root("file:///test", "Test")))
+		assertThatThrownBy(() -> result.roots().add(McpSchema.Root.builder("file:///test").name("Test").build()))
 			.isInstanceOf(UnsupportedOperationException.class);
 	}

 	@Test
 	void testListRootsWithEmptyResult() {

-		McpSchema.ListRootsResult emptyResult = new McpSchema.ListRootsResult(new ArrayList<>(), null);
+		McpSchema.ListRootsResult emptyResult = McpSchema.ListRootsResult.builder(new ArrayList<>()).build();

 		when(mockSession.sendRequest(eq(McpSchema.METHOD_ROOTS_LIST), any(McpSchema.PaginatedRequest.class),
 				any(TypeRef.class)))
@ -131,15 +136,16 @@ class McpSyncServerExchangeTests {
 		assertThat(result.nextCursor()).isNull();

 		// Verify that the returned list is unmodifiable
-		assertThatThrownBy(() -> result.roots().add(new McpSchema.Root("file:///test", "Test")))
+		assertThatThrownBy(() -> result.roots().add(McpSchema.Root.builder("file:///test").name("Test").build()))
 			.isInstanceOf(UnsupportedOperationException.class);
 	}

 	@Test
 	void testListRootsWithSpecificCursor() {

-		List<McpSchema.Root> roots = Arrays.asList(new McpSchema.Root("file:///home/user/project3", "Project 3"));
-		McpSchema.ListRootsResult result = new McpSchema.ListRootsResult(roots, "nextCursor");
+		List<McpSchema.Root> roots = Arrays
+			.asList(McpSchema.Root.builder("file:///home/user/project3").name("Project 3").build());
+		McpSchema.ListRootsResult result = McpSchema.ListRootsResult.builder(roots).nextCursor("nextCursor").build();

 		when(mockSession.sendRequest(eq(McpSchema.METHOD_ROOTS_LIST), eq(new McpSchema.PaginatedRequest("someCursor")),
 				any(TypeRef.class)))
@ -167,12 +173,14 @@ class McpSyncServerExchangeTests {
 	void testListRootsUnmodifiabilityAfterAccumulation() {

 		List<McpSchema.Root> page1Roots = new ArrayList<>(
-				Arrays.asList(new McpSchema.Root("file:///home/user/project1", "Project 1")));
+				Arrays.asList(McpSchema.Root.builder("file:///home/user/project1").name("Project 1").build()));
 		List<McpSchema.Root> page2Roots = new ArrayList<>(
-				Arrays.asList(new McpSchema.Root("file:///home/user/project2", "Project 2")));
+				Arrays.asList(McpSchema.Root.builder("file:///home/user/project2").name("Project 2").build()));

-		McpSchema.ListRootsResult page1Result = new McpSchema.ListRootsResult(page1Roots, "cursor1");
-		McpSchema.ListRootsResult page2Result = new McpSchema.ListRootsResult(page2Roots, null);
+		McpSchema.ListRootsResult page1Result = McpSchema.ListRootsResult.builder(page1Roots)
+			.nextCursor("cursor1")
+			.build();
+		McpSchema.ListRootsResult page2Result = McpSchema.ListRootsResult.builder(page2Roots).build();

 		when(mockSession.sendRequest(eq(McpSchema.METHOD_ROOTS_LIST), eq(new McpSchema.PaginatedRequest(null)),
 				any(TypeRef.class)))
@ -188,7 +196,7 @@ class McpSyncServerExchangeTests {
 		assertThat(result.roots()).hasSize(2);

 		// Verify that the returned list is unmodifiable
-		assertThatThrownBy(() -> result.roots().add(new McpSchema.Root("file:///test", "Test")))
+		assertThatThrownBy(() -> result.roots().add(McpSchema.Root.builder("file:///test").name("Test").build()))
 			.isInstanceOf(UnsupportedOperationException.class);

 		// Verify that clear() also throws UnsupportedOperationException
@ -221,10 +229,9 @@ class McpSyncServerExchangeTests {
 	@Test
 	void testLoggingNotificationWithAllowedLevel() {

-		McpSchema.LoggingMessageNotification notification = McpSchema.LoggingMessageNotification.builder()
-			.level(McpSchema.LoggingLevel.ERROR)
+		McpSchema.LoggingMessageNotification notification = McpSchema.LoggingMessageNotification
+			.builder(McpSchema.LoggingLevel.ERROR, "Test error message")
 			.logger("test-logger")
-			.data("Test error message")
 			.build();

 		when(mockSession.isNotificationForLevelAllowed(any())).thenReturn(Boolean.TRUE);
@ -243,10 +250,9 @@ class McpSyncServerExchangeTests {
 		asyncExchange.setMinLoggingLevel(McpSchema.LoggingLevel.DEBUG);
 		verify(mockSession, times(1)).setMinLoggingLevel(McpSchema.LoggingLevel.DEBUG);

-		McpSchema.LoggingMessageNotification debugNotification = McpSchema.LoggingMessageNotification.builder()
-			.level(McpSchema.LoggingLevel.DEBUG)
+		McpSchema.LoggingMessageNotification debugNotification = McpSchema.LoggingMessageNotification
+			.builder(McpSchema.LoggingLevel.DEBUG, "Debug message that should be filtered")
 			.logger("test-logger")
-			.data("Debug message that should be filtered")
 			.build();

 		when(mockSession.isNotificationForLevelAllowed(eq(McpSchema.LoggingLevel.DEBUG))).thenReturn(Boolean.TRUE);
@ -259,10 +265,9 @@ class McpSyncServerExchangeTests {
 		verify(mockSession, times(1)).sendNotification(eq(McpSchema.METHOD_NOTIFICATION_MESSAGE),
 				eq(debugNotification));

-		McpSchema.LoggingMessageNotification warningNotification = McpSchema.LoggingMessageNotification.builder()
-			.level(McpSchema.LoggingLevel.WARNING)
+		McpSchema.LoggingMessageNotification warningNotification = McpSchema.LoggingMessageNotification
+			.builder(McpSchema.LoggingLevel.WARNING, "Debug message that should be filtered")
 			.logger("test-logger")
-			.data("Debug message that should be filtered")
 			.build();

 		exchange.loggingNotification(warningNotification);
@ -275,10 +280,9 @@ class McpSyncServerExchangeTests {
 	@Test
 	void testLoggingNotificationWithSessionError() {

-		McpSchema.LoggingMessageNotification notification = McpSchema.LoggingMessageNotification.builder()
-			.level(McpSchema.LoggingLevel.ERROR)
+		McpSchema.LoggingMessageNotification notification = McpSchema.LoggingMessageNotification
+			.builder(McpSchema.LoggingLevel.ERROR, "Test error message")
 			.logger("test-logger")
-			.data("Test error message")
 			.build();

 		when(mockSession.isNotificationForLevelAllowed(any())).thenReturn(Boolean.TRUE);
@ -301,8 +305,8 @@ class McpSyncServerExchangeTests {
 		McpSyncServerExchange exchangeWithNullCapabilities = new McpSyncServerExchange(
 				asyncExchangeWithNullCapabilities);

-		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest.builder()
-			.message("Please provide your name")
+		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest
+			.builder("Please provide your name", Map.of("type", "object"))
 			.build();

 		assertThatThrownBy(() -> exchangeWithNullCapabilities.createElicitation(elicitRequest))
@ -324,8 +328,8 @@ class McpSyncServerExchangeTests {
 				mockSession, capabilitiesWithoutElicitation, clientInfo, McpTransportContext.EMPTY);
 		McpSyncServerExchange exchangeWithoutElicitation = new McpSyncServerExchange(asyncExchangeWithoutElicitation);

-		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest.builder()
-			.message("Please provide your name")
+		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest
+			.builder("Please provide your name", Map.of("type", "object"))
 			.build();

 		assertThatThrownBy(() -> exchangeWithoutElicitation.createElicitation(elicitRequest))
@ -355,17 +359,15 @@ class McpSyncServerExchangeTests {
 				java.util.Map.of("type", "number")));
 		requestedSchema.put("required", java.util.List.of("name"));

-		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest.builder()
-			.message("Please provide your personal information")
-			.requestedSchema(requestedSchema)
+		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest
+			.builder("Please provide your personal information", requestedSchema)
 			.build();

 		java.util.Map<String, Object> responseContent = new java.util.HashMap<>();
 		responseContent.put("name", "John Doe");
 		responseContent.put("age", 30);

-		McpSchema.ElicitResult expectedResult = McpSchema.ElicitResult.builder()
-			.message(McpSchema.ElicitResult.Action.ACCEPT)
+		McpSchema.ElicitResult expectedResult = McpSchema.ElicitResult.builder(McpSchema.ElicitResult.Action.ACCEPT)
 			.content(responseContent)
 			.build();

@ -392,12 +394,11 @@ class McpSyncServerExchangeTests {
 				capabilitiesWithElicitation, clientInfo, McpTransportContext.EMPTY);
 		McpSyncServerExchange exchangeWithElicitation = new McpSyncServerExchange(asyncExchangeWithElicitation);

-		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest.builder()
-			.message("Please provide sensitive information")
+		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest
+			.builder("Please provide sensitive information", Map.of("type", "object"))
 			.build();

-		McpSchema.ElicitResult expectedResult = McpSchema.ElicitResult.builder()
-			.message(McpSchema.ElicitResult.Action.DECLINE)
+		McpSchema.ElicitResult expectedResult = McpSchema.ElicitResult.builder(McpSchema.ElicitResult.Action.DECLINE)
 			.build();

 		when(mockSession.sendRequest(eq(McpSchema.METHOD_ELICITATION_CREATE), eq(elicitRequest), any(TypeRef.class)))
@ -420,12 +421,11 @@ class McpSyncServerExchangeTests {
 				capabilitiesWithElicitation, clientInfo, McpTransportContext.EMPTY);
 		McpSyncServerExchange exchangeWithElicitation = new McpSyncServerExchange(asyncExchangeWithElicitation);

-		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest.builder()
-			.message("Please provide your information")
+		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest
+			.builder("Please provide your information", Map.of("type", "object"))
 			.build();

-		McpSchema.ElicitResult expectedResult = McpSchema.ElicitResult.builder()
-			.message(McpSchema.ElicitResult.Action.CANCEL)
+		McpSchema.ElicitResult expectedResult = McpSchema.ElicitResult.builder(McpSchema.ElicitResult.Action.CANCEL)
 			.build();

 		when(mockSession.sendRequest(eq(McpSchema.METHOD_ELICITATION_CREATE), eq(elicitRequest), any(TypeRef.class)))
@ -448,8 +448,8 @@ class McpSyncServerExchangeTests {
 				capabilitiesWithElicitation, clientInfo, McpTransportContext.EMPTY);
 		McpSyncServerExchange exchangeWithElicitation = new McpSyncServerExchange(asyncExchangeWithElicitation);

-		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest.builder()
-			.message("Please provide your name")
+		McpSchema.ElicitRequest elicitRequest = McpSchema.ElicitRequest
+			.builder("Please provide your name", Map.of("type", "object"))
 			.build();

 		when(mockSession.sendRequest(eq(McpSchema.METHOD_ELICITATION_CREATE), eq(elicitRequest), any(TypeRef.class)))
@ -472,9 +472,10 @@ class McpSyncServerExchangeTests {
 		McpSyncServerExchange exchangeWithNullCapabilities = new McpSyncServerExchange(
 				asyncExchangeWithNullCapabilities);

-		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest.builder()
-			.messages(Arrays
-				.asList(new McpSchema.SamplingMessage(McpSchema.Role.USER, new McpSchema.TextContent("Hello, world!"))))
+		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest
+			.builder(Arrays.asList(McpSchema.SamplingMessage
+				.builder(McpSchema.Role.USER, McpSchema.TextContent.builder("Hello, world!").build())
+				.build()), 1000)
 			.build();

 		assertThatThrownBy(() -> exchangeWithNullCapabilities.createMessage(createMessageRequest))
@ -497,9 +498,10 @@ class McpSyncServerExchangeTests {
 				capabilitiesWithoutSampling, clientInfo, McpTransportContext.EMPTY);
 		McpSyncServerExchange exchangeWithoutSampling = new McpSyncServerExchange(asyncExchangeWithoutSampling);

-		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest.builder()
-			.messages(Arrays
-				.asList(new McpSchema.SamplingMessage(McpSchema.Role.USER, new McpSchema.TextContent("Hello, world!"))))
+		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest
+			.builder(Arrays.asList(McpSchema.SamplingMessage
+				.builder(McpSchema.Role.USER, McpSchema.TextContent.builder("Hello, world!").build())
+				.build()), 1000)
 			.build();

 		assertThatThrownBy(() -> exchangeWithoutSampling.createMessage(createMessageRequest))
@ -522,15 +524,15 @@ class McpSyncServerExchangeTests {
 				capabilitiesWithSampling, clientInfo, McpTransportContext.EMPTY);
 		McpSyncServerExchange exchangeWithSampling = new McpSyncServerExchange(asyncExchangeWithSampling);

-		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest.builder()
-			.messages(Arrays
-				.asList(new McpSchema.SamplingMessage(McpSchema.Role.USER, new McpSchema.TextContent("Hello, world!"))))
+		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest
+			.builder(Arrays.asList(McpSchema.SamplingMessage
+				.builder(McpSchema.Role.USER, McpSchema.TextContent.builder("Hello, world!").build())
+				.build()), 1000)
 			.build();

-		McpSchema.CreateMessageResult expectedResult = McpSchema.CreateMessageResult.builder()
-			.role(McpSchema.Role.ASSISTANT)
-			.content(new McpSchema.TextContent("Hello! How can I help you today?"))
-			.model("gpt-4")
+		McpSchema.CreateMessageResult expectedResult = McpSchema.CreateMessageResult
+			.builder(McpSchema.Role.ASSISTANT,
+					McpSchema.TextContent.builder("Hello! How can I help you today?").build(), "gpt-4")
 			.stopReason(McpSchema.CreateMessageResult.StopReason.END_TURN)
 			.build();

@ -560,16 +562,20 @@ class McpSyncServerExchangeTests {
 		McpSyncServerExchange exchangeWithSampling = new McpSyncServerExchange(asyncExchangeWithSampling);

 		// Create request with image content
-		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest.builder()
-			.messages(Arrays.asList(new McpSchema.SamplingMessage(McpSchema.Role.USER,
-					new McpSchema.ImageContent(null, "data:image/jpeg;base64,/9j/4AAQSkZJRgABAQEAYABgAAD...",
-							"image/jpeg"))))
+		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest.builder(Arrays.asList(
+				McpSchema.SamplingMessage
+					.builder(McpSchema.Role.USER,
+							McpSchema.ImageContent
+								.builder("data:image/jpeg;base64,/9j/4AAQSkZJRgABAQEAYABgAAD...", "image/jpeg")
+								.build())
+					.build()),
+				1000)
 			.build();

-		McpSchema.CreateMessageResult expectedResult = McpSchema.CreateMessageResult.builder()
-			.role(McpSchema.Role.ASSISTANT)
-			.content(new McpSchema.TextContent("I can see an image. It appears to be a photograph."))
-			.model("gpt-4-vision")
+		McpSchema.CreateMessageResult expectedResult = McpSchema.CreateMessageResult
+			.builder(McpSchema.Role.ASSISTANT,
+					McpSchema.TextContent.builder("I can see an image. It appears to be a photograph.").build(),
+					"gpt-4-vision")
 			.stopReason(McpSchema.CreateMessageResult.StopReason.END_TURN)
 			.build();

@ -595,9 +601,10 @@ class McpSyncServerExchangeTests {
 				capabilitiesWithSampling, clientInfo, McpTransportContext.EMPTY);
 		McpSyncServerExchange exchangeWithSampling = new McpSyncServerExchange(asyncExchangeWithSampling);

-		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest.builder()
-			.messages(Arrays
-				.asList(new McpSchema.SamplingMessage(McpSchema.Role.USER, new McpSchema.TextContent("Hello"))))
+		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest.builder(Arrays.asList(
+				McpSchema.SamplingMessage.builder(McpSchema.Role.USER, McpSchema.TextContent.builder("Hello").build())
+					.build()),
+				1000)
 			.build();

 		when(mockSession.sendRequest(eq(McpSchema.METHOD_SAMPLING_CREATE_MESSAGE), eq(createMessageRequest),
@ -620,16 +627,17 @@ class McpSyncServerExchangeTests {
 				capabilitiesWithSampling, clientInfo, McpTransportContext.EMPTY);
 		McpSyncServerExchange exchangeWithSampling = new McpSyncServerExchange(asyncExchangeWithSampling);

-		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest.builder()
-			.messages(Arrays.asList(new McpSchema.SamplingMessage(McpSchema.Role.USER,
-					new McpSchema.TextContent("What files are available?"))))
+		McpSchema.CreateMessageRequest createMessageRequest = McpSchema.CreateMessageRequest
+			.builder(Arrays.asList(McpSchema.SamplingMessage
+				.builder(McpSchema.Role.USER, McpSchema.TextContent.builder("What files are available?").build())
+				.build()), 1000)
 			.includeContext(McpSchema.CreateMessageRequest.ContextInclusionStrategy.ALL_SERVERS)
 			.build();

-		McpSchema.CreateMessageResult expectedResult = McpSchema.CreateMessageResult.builder()
-			.role(McpSchema.Role.ASSISTANT)
-			.content(new McpSchema.TextContent("Based on the available context, I can see several files..."))
-			.model("gpt-4")
+		McpSchema.CreateMessageResult expectedResult = McpSchema.CreateMessageResult
+			.builder(McpSchema.Role.ASSISTANT,
+					McpSchema.TextContent.builder("Based on the available context, I can see several files...").build(),
+					"gpt-4")
 			.stopReason(McpSchema.CreateMessageResult.StopReason.END_TURN)
 			.build();

--- a/mcp-core/src/test/java/io/modelcontextprotocol/server/ResourceTemplateListingTest.java
+++ b/mcp-core/src/test/java/io/modelcontextprotocol/server/ResourceTemplateListingTest.java
@ -41,24 +41,12 @@ public class ResourceTemplateListingTest {
 	void testResourceListingWithMixedResources() {
 		// Create resource list with both regular and template resources
 		List<McpSchema.Resource> allResources = List.of(
-				McpSchema.Resource.builder()
-					.uri("file:///test/doc1.txt")
-					.name("Document 1")
+				McpSchema.Resource.builder("file:///test/doc1.txt", "Document 1").mimeType("text/plain").build(),
+				McpSchema.Resource.builder("file:///test/doc2.txt", "Document 2").mimeType("text/plain").build(),
+				McpSchema.Resource.builder("file:///test/{type}/document.txt", "Typed Document")
 					.mimeType("text/plain")
 					.build(),
-				McpSchema.Resource.builder()
-					.uri("file:///test/doc2.txt")
-					.name("Document 2")
-					.mimeType("text/plain")
-					.build(),
-				McpSchema.Resource.builder()
-					.uri("file:///test/{type}/document.txt")
-					.name("Typed Document")
-					.mimeType("text/plain")
-					.build(),
-				McpSchema.Resource.builder()
-					.uri("file:///users/{userId}/files/{fileId}")
-					.name("User File")
+				McpSchema.Resource.builder("file:///users/{userId}/files/{fileId}", "User File")
 					.mimeType("text/plain")
 					.build());

@ -77,20 +65,18 @@ public class ResourceTemplateListingTest {
 	void testResourceTemplatesListedSeparately() {
 		// Create mixed resources
 		List<McpSchema.Resource> resources = List.of(
-				McpSchema.Resource.builder()
-					.uri("file:///test/regular.txt")
-					.name("Regular Resource")
+				McpSchema.Resource.builder("file:///test/regular.txt", "Regular Resource")
 					.mimeType("text/plain")
 					.build(),
-				McpSchema.Resource.builder()
-					.uri("file:///test/user/{userId}/profile.txt")
-					.name("User Profile")
+				McpSchema.Resource.builder("file:///test/user/{userId}/profile.txt", "User Profile")
 					.mimeType("text/plain")
 					.build());

 		// Create explicit resource template
-		McpSchema.ResourceTemplate explicitTemplate = new McpSchema.ResourceTemplate(
-				"file:///test/document/{docId}/content.txt", "Document Template", null, "text/plain", null);
+		McpSchema.ResourceTemplate explicitTemplate = McpSchema.ResourceTemplate
+			.builder("file:///test/document/{docId}/content.txt", "Document Template")
+			.mimeType("text/plain")
+			.build();

 		// Filter regular resources (those without template parameters)
 		List<McpSchema.Resource> regularResources = resources.stream()
@ -100,8 +86,11 @@ public class ResourceTemplateListingTest {
 		// Extract template resources (those with template parameters)
 		List<McpSchema.ResourceTemplate> templateResources = resources.stream()
 			.filter(resource -> resource.uri().contains("{"))
-			.map(resource -> new McpSchema.ResourceTemplate(resource.uri(), resource.name(), resource.description(),
-					resource.mimeType(), resource.annotations()))
+			.map(resource -> McpSchema.ResourceTemplate.builder(resource.uri(), resource.name())
+				.description(resource.description())
+				.mimeType(resource.mimeType())
+				.annotations(resource.annotations())
+				.build())
 			.collect(Collectors.toList());

 		// Verify regular resources list
--- a/mcp-core/src/test/java/io/modelcontextprotocol/server/SyncToolSpecificationBuilderTest.java
+++ b/mcp-core/src/test/java/io/modelcontextprotocol/server/SyncToolSpecificationBuilderTest.java
@ -39,12 +39,12 @@ class SyncToolSpecificationBuilderTest {
 	@Test
 	void builderShouldCreateValidSyncToolSpecification() {

-		Tool tool = Tool.builder().name("test-tool").title("A test tool").inputSchema(EMPTY_JSON_SCHEMA).build();
+		Tool tool = Tool.builder("test-tool", EMPTY_JSON_SCHEMA).title("A test tool").build();

 		McpServerFeatures.SyncToolSpecification specification = McpServerFeatures.SyncToolSpecification.builder()
 			.tool(tool)
 			.callHandler((exchange, request) -> CallToolResult.builder()
-				.content(List.of(new TextContent("Test result")))
+				.content(List.of(TextContent.builder("Test result").build()))
 				.isError(false)
 				.build())
 			.build();
@ -63,7 +63,7 @@ class SyncToolSpecificationBuilderTest {

 	@Test
 	void builderShouldThrowExceptionWhenCallToolIsNull() {
-		Tool tool = Tool.builder().name("test-tool").description("A test tool").inputSchema(EMPTY_JSON_SCHEMA).build();
+		Tool tool = Tool.builder("test-tool", EMPTY_JSON_SCHEMA).description("A test tool").build();

 		assertThatThrownBy(() -> McpServerFeatures.SyncToolSpecification.builder().tool(tool).build())
 			.isInstanceOf(IllegalArgumentException.class)
@ -72,7 +72,7 @@ class SyncToolSpecificationBuilderTest {

 	@Test
 	void builderShouldAllowMethodChaining() {
-		Tool tool = Tool.builder().name("test-tool").description("A test tool").inputSchema(EMPTY_JSON_SCHEMA).build();
+		Tool tool = Tool.builder("test-tool", EMPTY_JSON_SCHEMA).description("A test tool").build();
 		McpServerFeatures.SyncToolSpecification.Builder builder = McpServerFeatures.SyncToolSpecification.builder();

 		// Then - verify method chaining returns the same builder instance
@ -84,11 +84,7 @@ class SyncToolSpecificationBuilderTest {

 	@Test
 	void builtSpecificationShouldExecuteCallToolCorrectly() {
-		Tool tool = Tool.builder()
-			.name("calculator")
-			.description("Simple calculator")
-			.inputSchema(EMPTY_JSON_SCHEMA)
-			.build();
+		Tool tool = Tool.builder("calculator", EMPTY_JSON_SCHEMA).description("Simple calculator").build();
 		String expectedResult = "42";

 		McpServerFeatures.SyncToolSpecification specification = McpServerFeatures.SyncToolSpecification.builder()
@ -96,13 +92,13 @@ class SyncToolSpecificationBuilderTest {
 			.callHandler((exchange, request) -> {
 				// Simple test implementation
 				return CallToolResult.builder()
-					.content(List.of(new TextContent(expectedResult)))
+					.content(List.of(TextContent.builder(expectedResult).build()))
 					.isError(false)
 					.build();
 			})
 			.build();

-		CallToolRequest request = new CallToolRequest("calculator", Map.of());
+		CallToolRequest request = CallToolRequest.builder("calculator").build();
 		CallToolResult result = specification.callHandler().apply(null, request);

 		assertThat(result).isNotNull();
@ -138,7 +134,7 @@ class SyncToolSpecificationBuilderTest {

 		@Test
 		void defaultShouldThrowOnInvalidName() {
-			Tool invalidTool = Tool.builder().name("invalid tool name").build();
+			Tool invalidTool = Tool.builder("invalid tool name", EMPTY_JSON_SCHEMA).build();

 			assertThatThrownBy(
 					() -> McpServer.sync(transportProvider).toolCall(invalidTool, (exchange, request) -> null))
@ -149,7 +145,7 @@ class SyncToolSpecificationBuilderTest {
 		@Test
 		void lenientDefaultShouldLogOnInvalidName() {
 			System.setProperty(ToolNameValidator.STRICT_VALIDATION_PROPERTY, "false");
-			Tool invalidTool = Tool.builder().name("invalid tool name").build();
+			Tool invalidTool = Tool.builder("invalid tool name", EMPTY_JSON_SCHEMA).build();

 			assertThatCode(() -> McpServer.sync(transportProvider).toolCall(invalidTool, (exchange, request) -> null))
 				.doesNotThrowAnyException();
@ -158,7 +154,7 @@ class SyncToolSpecificationBuilderTest {

 		@Test
 		void lenientConfigurationShouldLogOnInvalidName() {
-			Tool invalidTool = Tool.builder().name("invalid tool name").build();
+			Tool invalidTool = Tool.builder("invalid tool name", EMPTY_JSON_SCHEMA).build();

 			assertThatCode(() -> McpServer.sync(transportProvider)
 				.strictToolNameValidation(false)
@ -169,7 +165,7 @@ class SyncToolSpecificationBuilderTest {
 		@Test
 		void serverConfigurationShouldOverrideDefault() {
 			System.setProperty(ToolNameValidator.STRICT_VALIDATION_PROPERTY, "false");
-			Tool invalidTool = Tool.builder().name("invalid tool name").build();
+			Tool invalidTool = Tool.builder("invalid tool name", EMPTY_JSON_SCHEMA).build();

 			assertThatThrownBy(() -> McpServer.sync(transportProvider)
 				.strictToolNameValidation(true)
--- a/mcp-core/src/test/java/io/modelcontextprotocol/spec/JSONRPCRequestMcpValidationTest.java
+++ b/mcp-core/src/test/java/io/modelcontextprotocol/spec/JSONRPCRequestMcpValidationTest.java
@ -20,7 +20,7 @@ public class JSONRPCRequestMcpValidationTest {
 	@Test
 	public void testValidStringId() {
 		assertDoesNotThrow(() -> {
-			var request = new McpSchema.JSONRPCRequest("2.0", "test/method", "string-id", null);
+			var request = new McpSchema.JSONRPCRequest("test/method", "string-id");
 			assertEquals("string-id", request.id());
 		});
 	}
@ -28,7 +28,7 @@ public class JSONRPCRequestMcpValidationTest {
 	@Test
 	public void testValidIntegerId() {
 		assertDoesNotThrow(() -> {
-			var request = new McpSchema.JSONRPCRequest("2.0", "test/method", 123, null);
+			var request = new McpSchema.JSONRPCRequest("test/method", 123);
 			assertEquals(123, request.id());
 		});
 	}
@ -36,7 +36,7 @@ public class JSONRPCRequestMcpValidationTest {
 	@Test
 	public void testValidLongId() {
 		assertDoesNotThrow(() -> {
-			var request = new McpSchema.JSONRPCRequest("2.0", "test/method", 123L, null);
+			var request = new McpSchema.JSONRPCRequest("test/method", 123L);
 			assertEquals(123L, request.id());
 		});
 	}
@ -44,7 +44,7 @@ public class JSONRPCRequestMcpValidationTest {
 	@Test
 	public void testNullIdThrowsException() {
 		IllegalArgumentException exception = assertThrows(IllegalArgumentException.class, () -> {
-			new McpSchema.JSONRPCRequest("2.0", "test/method", null, null);
+			new McpSchema.JSONRPCRequest("test/method", null);
 		});

 		assertTrue(exception.getMessage().contains("MCP requests MUST include an ID"));
@ -54,7 +54,7 @@ public class JSONRPCRequestMcpValidationTest {
 	@Test
 	public void testDoubleIdTypeThrowsException() {
 		IllegalArgumentException exception = assertThrows(IllegalArgumentException.class, () -> {
-			new McpSchema.JSONRPCRequest("2.0", "test/method", 123.45, null);
+			new McpSchema.JSONRPCRequest("test/method", 123.45);
 		});

 		assertTrue(exception.getMessage().contains("MCP requests MUST have an ID that is either a string or integer"));
@ -63,7 +63,7 @@ public class JSONRPCRequestMcpValidationTest {
 	@Test
 	public void testBooleanIdThrowsException() {
 		IllegalArgumentException exception = assertThrows(IllegalArgumentException.class, () -> {
-			new McpSchema.JSONRPCRequest("2.0", "test/method", true, null);
+			new McpSchema.JSONRPCRequest("test/method", true);
 		});

 		assertTrue(exception.getMessage().contains("MCP requests MUST have an ID that is either a string or integer"));
@ -72,7 +72,7 @@ public class JSONRPCRequestMcpValidationTest {
 	@Test
 	public void testArrayIdThrowsException() {
 		IllegalArgumentException exception = assertThrows(IllegalArgumentException.class, () -> {
-			new McpSchema.JSONRPCRequest("2.0", "test/method", new String[] { "array" }, null);
+			new McpSchema.JSONRPCRequest("test/method", new String[] { "array" });
 		});

 		assertTrue(exception.getMessage().contains("MCP requests MUST have an ID that is either a string or integer"));
@ -81,7 +81,7 @@ public class JSONRPCRequestMcpValidationTest {
 	@Test
 	public void testObjectIdThrowsException() {
 		IllegalArgumentException exception = assertThrows(IllegalArgumentException.class, () -> {
-			new McpSchema.JSONRPCRequest("2.0", "test/method", new Object(), null);
+			new McpSchema.JSONRPCRequest("test/method", new Object());
 		});

 		assertTrue(exception.getMessage().contains("MCP requests MUST have an ID that is either a string or integer"));
--- a/mcp-core/src/test/java/io/modelcontextprotocol/spec/McpClientSessionTests.java
+++ b/mcp-core/src/test/java/io/modelcontextprotocol/spec/McpClientSessionTests.java
@ -55,8 +55,7 @@ class McpClientSessionTests {
 		// Verify response handling
 		StepVerifier.create(responseMono).then(() -> {
 			McpSchema.JSONRPCRequest request = transport.getLastSentMessageAsRequest();
-			transport.simulateIncomingMessage(
-					new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION, request.id(), responseData, null));
+			transport.simulateIncomingMessage(McpSchema.JSONRPCResponse.result(request.id(), responseData));
 		}).consumeNextWith(response -> {
 			// Verify the request was sent
 			McpSchema.JSONRPCMessage sentMessage = transport.getLastSentMessageAsRequest();
@ -84,9 +83,8 @@ class McpClientSessionTests {
 			McpSchema.JSONRPCRequest request = transport.getLastSentMessageAsRequest();
 			// Simulate error response
 			McpSchema.JSONRPCResponse.JSONRPCError error = new McpSchema.JSONRPCResponse.JSONRPCError(
-					McpSchema.ErrorCodes.METHOD_NOT_FOUND, "Method not found", null);
-			transport.simulateIncomingMessage(
-					new McpSchema.JSONRPCResponse(McpSchema.JSONRPC_VERSION, request.id(), null, error));
+					McpSchema.ErrorCodes.METHOD_NOT_FOUND, "Method not found");
+			transport.simulateIncomingMessage(McpSchema.JSONRPCResponse.error(request.id(), error));
 		}).expectError(McpError.class).verify();

 		session.close();
@ -140,8 +138,7 @@ class McpClientSessionTests {
 		var session = new McpClientSession(TIMEOUT, transport, requestHandlers, Map.of(), Function.identity());

 		// Simulate incoming request
-		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION, ECHO_METHOD,
-				"test-id", echoMessage);
+		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(ECHO_METHOD, "test-id", echoMessage);
 		transport.simulateIncomingMessage(request);

 		// Verify response
@ -166,8 +163,8 @@ class McpClientSessionTests {
 		// Simulate incoming notification from the server
 		Map<String, Object> notificationParams = Map.of("status", "ready");

-		McpSchema.JSONRPCNotification notification = new McpSchema.JSONRPCNotification(McpSchema.JSONRPC_VERSION,
-				TEST_NOTIFICATION, notificationParams);
+		McpSchema.JSONRPCNotification notification = new McpSchema.JSONRPCNotification(TEST_NOTIFICATION,
+				notificationParams);

 		transport.simulateIncomingMessage(notification);

@ -186,8 +183,7 @@ class McpClientSessionTests {
 				Function.identity());

 		// Simulate incoming request for unknown method
-		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION, "unknown.method",
-				"test-id", null);
+		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest("unknown.method", "test-id");
 		transport.simulateIncomingMessage(request);

 		// Verify error response
@ -214,8 +210,7 @@ class McpClientSessionTests {
 				Function.identity());

 		// Simulate incoming request that will trigger the error
-		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION, testMethod,
-				"test-id", null);
+		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(testMethod, "test-id");
 		transport.simulateIncomingMessage(request);

 		// Verify: The response should contain the custom error from McpError
@ -242,8 +237,7 @@ class McpClientSessionTests {
 				Function.identity());

 		// Simulate incoming request that will trigger the error
-		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION, testMethod,
-				"test-id", null);
+		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(testMethod, "test-id");
 		transport.simulateIncomingMessage(request);

 		// Verify: The response should contain INTERNAL_ERROR with aggregated exception
@ -276,8 +270,7 @@ class McpClientSessionTests {
 				Function.identity());

 		// Simulate incoming request that will trigger the error
-		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(McpSchema.JSONRPC_VERSION, testMethod,
-				"test-id", null);
+		McpSchema.JSONRPCRequest request = new McpSchema.JSONRPCRequest(testMethod, "test-id");
 		transport.simulateIncomingMessage(request);

 		// Verify: The response should contain INTERNAL_ERROR with full exception chain
--- a/mcp-core/src/test/java/io/modelcontextprotocol/spec/PromptReferenceEqualsTest.java
+++ b/mcp-core/src/test/java/io/modelcontextprotocol/spec/PromptReferenceEqualsTest.java
@ -18,10 +18,8 @@ class PromptReferenceEqualsTest {

 	@Test
 	void testEqualsWithSameIdentifierAndType() {
-		McpSchema.PromptReference ref1 = new McpSchema.PromptReference(PromptReference.TYPE, "test-prompt",
-				"Test Title");
-		McpSchema.PromptReference ref2 = new McpSchema.PromptReference(PromptReference.TYPE, "test-prompt",
-				"Different Title");
+		McpSchema.PromptReference ref1 = PromptReference.builder("test-prompt").title("Test Title").build();
+		McpSchema.PromptReference ref2 = PromptReference.builder("test-prompt").title("Different Title").build();

 		assertTrue(ref1.equals(ref2), "PromptReferences with same identifier and type should be equal");
 		assertEquals(ref1.hashCode(), ref2.hashCode(), "Equal objects should have same hash code");
@ -29,35 +27,22 @@ class PromptReferenceEqualsTest {

 	@Test
 	void testEqualsWithDifferentIdentifier() {
-		McpSchema.PromptReference ref1 = new McpSchema.PromptReference(PromptReference.TYPE, "test-prompt-1",
-				"Test Title");
-		McpSchema.PromptReference ref2 = new McpSchema.PromptReference(PromptReference.TYPE, "test-prompt-2",
-				"Test Title");
+		McpSchema.PromptReference ref1 = PromptReference.builder("test-prompt-1").title("Test Title").build();
+		McpSchema.PromptReference ref2 = PromptReference.builder("test-prompt-2").title("Test Title").build();

 		assertFalse(ref1.equals(ref2), "PromptReferences with different identifiers should not be equal");
 	}

-	@Test
-	void testEqualsWithDifferentType() {
-		McpSchema.PromptReference ref1 = new McpSchema.PromptReference(PromptReference.TYPE, "test-prompt",
-				"Test Title");
-		McpSchema.PromptReference ref2 = new McpSchema.PromptReference("ref/other", "test-prompt", "Test Title");
-
-		assertFalse(ref1.equals(ref2), "PromptReferences with different types should not be equal");
-	}
-
 	@Test
 	void testEqualsWithNull() {
-		McpSchema.PromptReference ref1 = new McpSchema.PromptReference(PromptReference.TYPE, "test-prompt",
-				"Test Title");
+		McpSchema.PromptReference ref1 = PromptReference.builder("test-prompt").title("Test Title").build();

 		assertFalse(ref1.equals(null), "PromptReference should not be equal to null");
 	}

 	@Test
 	void testEqualsWithDifferentClass() {
-		McpSchema.PromptReference ref1 = new McpSchema.PromptReference(PromptReference.TYPE, "test-prompt",
-				"Test Title");
+		McpSchema.PromptReference ref1 = PromptReference.builder("test-prompt").title("Test Title").build();
 		String other = "not a PromptReference";

 		assertFalse(ref1.equals(other), "PromptReference should not be equal to different class");
@ -65,17 +50,16 @@ class PromptReferenceEqualsTest {

 	@Test
 	void testEqualsWithSameInstance() {
-		McpSchema.PromptReference ref1 = new McpSchema.PromptReference(PromptReference.TYPE, "test-prompt",
-				"Test Title");
+		McpSchema.PromptReference ref1 = PromptReference.builder("test-prompt").title("Test Title").build();

 		assertTrue(ref1.equals(ref1), "PromptReference should be equal to itself");
 	}

 	@Test
 	void testEqualsIgnoresTitle() {
-		McpSchema.PromptReference ref1 = new McpSchema.PromptReference(PromptReference.TYPE, "test-prompt", "Title 1");
-		McpSchema.PromptReference ref2 = new McpSchema.PromptReference(PromptReference.TYPE, "test-prompt", "Title 2");
-		McpSchema.PromptReference ref3 = new McpSchema.PromptReference(PromptReference.TYPE, "test-prompt", null);
+		McpSchema.PromptReference ref1 = PromptReference.builder("test-prompt").title("Title 1").build();
+		McpSchema.PromptReference ref2 = PromptReference.builder("test-prompt").title("Title 2").build();
+		McpSchema.PromptReference ref3 = new PromptReference("test-prompt");

 		assertTrue(ref1.equals(ref2), "PromptReferences should be equal regardless of title");
 		assertTrue(ref1.equals(ref3), "PromptReferences should be equal even when one has null title");
@ -84,14 +68,11 @@ class PromptReferenceEqualsTest {

 	@Test
 	void testHashCodeConsistency() {
-		McpSchema.PromptReference ref1 = new McpSchema.PromptReference(PromptReference.TYPE, "test-prompt",
-				"Test Title");
-		McpSchema.PromptReference ref2 = new McpSchema.PromptReference(PromptReference.TYPE, "test-prompt",
-				"Different Title");
+		McpSchema.PromptReference ref1 = PromptReference.builder("test-prompt").title("Test Title").build();
+		McpSchema.PromptReference ref2 = PromptReference.builder("test-prompt").title("Different Title").build();

 		assertEquals(ref1.hashCode(), ref2.hashCode(), "Objects that are equal should have the same hash code");

-		// Call hashCode multiple times to ensure consistency
 		int hashCode1 = ref1.hashCode();
 		int hashCode2 = ref1.hashCode();
 		assertEquals(hashCode1, hashCode2, "Hash code should be consistent across multiple calls");
--- a/mcp-core/src/test/java/io/modelcontextprotocol/spec/json/gson/GsonMcpJsonMapperTests.java
+++ b/mcp-core/src/test/java/io/modelcontextprotocol/spec/json/gson/GsonMcpJsonMapperTests.java
@ -105,13 +105,13 @@ class GsonMcpJsonMapperTests {
 		var gsonMapper = new GsonMcpJsonMapper();

 		// Tool builder parsing of input/output schema strings
-		var tool = McpSchema.Tool.builder().name("echo").description("Echo tool").inputSchema(gsonMapper, """
+		var tool = McpSchema.Tool.builder("echo", gsonMapper, """
 				{
 				  "type": "object",
 				  "properties": { "x": { "type": "integer" } },
 				  "required": ["x"]
 				}
-				""").outputSchema(gsonMapper, """
+				""").description("Echo tool").outputSchema(gsonMapper, """
 				{
 				  "type": "object",
 				  "properties": { "y": { "type": "string" } }
--- a/mcp-core/src/test/java/io/modelcontextprotocol/util/ToolInputValidatorTests.java
+++ b/mcp-core/src/test/java/io/modelcontextprotocol/util/ToolInputValidatorTests.java
@ -16,10 +16,7 @@ import org.junit.jupiter.api.Test;

 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.ArgumentMatchers.any;
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.never;
-import static org.mockito.Mockito.verify;
-import static org.mockito.Mockito.when;
+import static org.mockito.Mockito.*;

 /**
 * Tests for {@link ToolInputValidator}.
@ -33,13 +30,9 @@ class ToolInputValidatorTests {
 	private final Map<String, Object> inputSchema = Map.of("type", "object", "properties",
 			Map.of("name", Map.of("type", "string")), "required", List.of("name"));

-	private final Tool toolWithSchema = Tool.builder()
-		.name("test-tool")
-		.description("Test tool")
-		.inputSchema(inputSchema)
-		.build();
+	private final Tool toolWithSchema = Tool.builder("test-tool", inputSchema).description("Test tool").build();

-	private final Tool toolWithoutSchema = Tool.builder().name("test-tool").description("Test tool").build();
+	private final Tool toolWithoutSchema = Tool.builder("test-tool").description("Test tool").build();

 	@Test
 	void validate_whenDisabled_returnsNull() {
@ -51,10 +44,12 @@ class ToolInputValidatorTests {

 	@Test
 	void validate_whenNoSchema_returnsNull() {
+		when(validator.validate(any(), any())).thenReturn(ValidationResponse.asValid(null));
+
 		CallToolResult result = ToolInputValidator.validate(toolWithoutSchema, Map.of("name", "test"), true, validator);

 		assertThat(result).isNull();
-		verify(validator, never()).validate(any(), any());
+		verify(validator).validate(any(), any());
 	}

 	@Test