feat: Introduce McpJsonMapper interface to decouple from Jackson (#543)

This pull request creates two modules, `mcp-json` and `mcp-json-jackson`. It removes the `com.fasterxml.jackson.core:jackson-databind` and `com.networknt:json-schema-validator` dependencies from the `mcp` module. The `mcp` module now only depends on `com.fasterxml.jackson.core:jackson-annotations`.

To use Jackson, you have to add `mcp-jackson` to your dependencies in addition to `mcp`. I added the dependency `mcp-jackson` to both `mcp-spring-mvc` and `mcp-spring-webflux` to avoid a breaking change in those modules.

It provides two [SPI](https://docs.oracle.com/javase/tutorial/sound/SPI-intro.html) `JsonSchemaValidatorSupplier` and `JacksonJsonSchemaValidatorSupplier` to allow easy replacement for consumers who don't want to use Jackson.

This pull request also ensures no `McpJsonMapper` is instantiated if one is provided via a builder method. Only if the builders don't receive a `McpJsonMapper` mapper, one is instantiated in the `build` method of the builder.
The logic behind this is to allow frameworks to provide a `McpJsonMapper` mapper singleton implementation and feed it to the builders without paying the price of instantiating `McpJsonMappers`, which will not be used. The goal is to be able to use the `ObjectMapper` singleton of an application also for the MCP code.

Signed-off-by: Christian Tzolov <christian.tzolov@broadcom.com>

mcp-test/src/main/java/io/modelcontextprotocol/AbstractMcpClientServerIntegrationTests.java

@@ -54,6 +54,7 @@ import org.junit.jupiter.params.provider.ValueSource;
 import reactor.core.publisher.Mono;
 import reactor.test.StepVerifier;
 
+import static io.modelcontextprotocol.utils.ToolsUtils.EMPTY_JSON_SCHEMA;
 import static net.javacrumbs.jsonunit.assertj.JsonAssertions.assertThatJson;
 import static net.javacrumbs.jsonunit.assertj.JsonAssertions.json;
 import static org.assertj.core.api.Assertions.assertThat;
@@ -81,7 +82,6 @@ public abstract class AbstractMcpClientServerIntegrationTests {
 		var server = prepareAsyncServerBuilder().serverInfo("test-server", "1.0.0")
 			.requestTimeout(Duration.ofSeconds(1000))
 			.build();
-
 		try (
 				// Create client without sampling capabilities
 				var client = clientBuilder.clientInfo(new McpSchema.Implementation("Sample " + "client", "0.0.0"))
@@ -106,7 +106,7 @@ public abstract class AbstractMcpClientServerIntegrationTests {
 		var clientBuilder = clientBuilders.get(clientType);
 
 		McpServerFeatures.AsyncToolSpecification tool = McpServerFeatures.AsyncToolSpecification.builder()
-			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(emptyJsonSchema).build())
+			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
 			.callHandler((exchange, request) -> {
 				return exchange.createMessage(mock(McpSchema.CreateMessageRequest.class))
 					.then(Mono.just(mock(CallToolResult.class)));
@@ -155,7 +155,7 @@ public abstract class AbstractMcpClientServerIntegrationTests {
 		AtomicReference<CreateMessageResult> samplingResult = new AtomicReference<>();
 
 		McpServerFeatures.AsyncToolSpecification tool = McpServerFeatures.AsyncToolSpecification.builder()
-			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(emptyJsonSchema).build())
+			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
 			.callHandler((exchange, request) -> {
 
 				var createMessageRequest = McpSchema.CreateMessageRequest.builder()
@@ -233,7 +233,7 @@ public abstract class AbstractMcpClientServerIntegrationTests {
 		AtomicReference<CreateMessageResult> samplingResult = new AtomicReference<>();
 
 		McpServerFeatures.AsyncToolSpecification tool = McpServerFeatures.AsyncToolSpecification.builder()
-			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(emptyJsonSchema).build())
+			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
 			.callHandler((exchange, request) -> {
 
 				var createMessageRequest = McpSchema.CreateMessageRequest.builder()
@@ -307,7 +307,7 @@ public abstract class AbstractMcpClientServerIntegrationTests {
 				null);
 
 		McpServerFeatures.AsyncToolSpecification tool = McpServerFeatures.AsyncToolSpecification.builder()
-			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(emptyJsonSchema).build())
+			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
 			.callHandler((exchange, request) -> {
 
 				var createMessageRequest = McpSchema.CreateMessageRequest.builder()
@@ -357,7 +357,7 @@ public abstract class AbstractMcpClientServerIntegrationTests {
 		var clientBuilder = clientBuilders.get(clientType);
 
 		McpServerFeatures.AsyncToolSpecification tool = McpServerFeatures.AsyncToolSpecification.builder()
-			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(emptyJsonSchema).build())
+			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
 			.callHandler((exchange, request) -> exchange.createElicitation(mock(ElicitRequest.class))
 				.then(Mono.just(mock(CallToolResult.class))))
 			.build();
@@ -400,7 +400,7 @@ public abstract class AbstractMcpClientServerIntegrationTests {
 				null);
 
 		McpServerFeatures.AsyncToolSpecification tool = McpServerFeatures.AsyncToolSpecification.builder()
-			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(emptyJsonSchema).build())
+			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
 			.callHandler((exchange, request) -> {
 
 				var elicitationRequest = McpSchema.ElicitRequest.builder()
@@ -457,7 +457,7 @@ public abstract class AbstractMcpClientServerIntegrationTests {
 		AtomicReference<ElicitResult> resultRef = new AtomicReference<>();
 
 		McpServerFeatures.AsyncToolSpecification tool = McpServerFeatures.AsyncToolSpecification.builder()
-			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(emptyJsonSchema).build())
+			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
 			.callHandler((exchange, request) -> {
 
 				var elicitationRequest = McpSchema.ElicitRequest.builder()
@@ -528,7 +528,7 @@ public abstract class AbstractMcpClientServerIntegrationTests {
 		AtomicReference<ElicitResult> resultRef = new AtomicReference<>();
 
 		McpServerFeatures.AsyncToolSpecification tool = McpServerFeatures.AsyncToolSpecification.builder()
-			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(emptyJsonSchema).build())
+			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
 			.callHandler((exchange, request) -> {
 
 				var elicitationRequest = ElicitRequest.builder()
@@ -626,7 +626,7 @@ public abstract class AbstractMcpClientServerIntegrationTests {
 		var clientBuilder = clientBuilders.get(clientType);
 
 		McpServerFeatures.SyncToolSpecification tool = McpServerFeatures.SyncToolSpecification.builder()
-			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(emptyJsonSchema).build())
+			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
 			.callHandler((exchange, request) -> {
 
 				exchange.listRoots(); // try to list roots
@@ -757,14 +757,6 @@ public abstract class AbstractMcpClientServerIntegrationTests {
 	// ---------------------------------------
 	// Tools Tests
 	// ---------------------------------------
-	String emptyJsonSchema = """
-			{
-				"$schema": "http://json-schema.org/draft-07/schema#",
-				"type": "object",
-				"properties": {}
-			}
-			""";
-
 	@ParameterizedTest(name = "{0} : {displayName} ")
 	@ValueSource(strings = { "httpclient", "webflux" })
 	void testToolCallSuccess(String clientType) {
@@ -774,7 +766,7 @@ public abstract class AbstractMcpClientServerIntegrationTests {
 		var responseBodyIsNullOrBlank = new AtomicBoolean(false);
 		var callResponse = new McpSchema.CallToolResult(List.of(new McpSchema.TextContent("CALL RESPONSE")), null);
 		McpServerFeatures.SyncToolSpecification tool1 = McpServerFeatures.SyncToolSpecification.builder()
-			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(emptyJsonSchema).build())
+			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
 			.callHandler((exchange, request) -> {
 
 				try {
@@ -828,7 +820,7 @@ public abstract class AbstractMcpClientServerIntegrationTests {
 				.tool(Tool.builder()
 					.name("tool1")
 					.description("tool1 description")
-					.inputSchema(emptyJsonSchema)
+					.inputSchema(EMPTY_JSON_SCHEMA)
 					.build())
 				.callHandler((exchange, request) -> {
 					// We trigger a timeout on blocking read, raising an exception
@@ -867,7 +859,7 @@ public abstract class AbstractMcpClientServerIntegrationTests {
 		var expectedCallResponse = new McpSchema.CallToolResult(
 				List.of(new McpSchema.TextContent("CALL RESPONSE; ctx=value")), null);
 		McpServerFeatures.SyncToolSpecification tool1 = McpServerFeatures.SyncToolSpecification.builder()
-			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(emptyJsonSchema).build())
+			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
 			.callHandler((exchange, request) -> {
 
 				McpTransportContext transportContext = exchange.transportContext();
@@ -919,7 +911,7 @@ public abstract class AbstractMcpClientServerIntegrationTests {
 
 		var callResponse = new McpSchema.CallToolResult(List.of(new McpSchema.TextContent("CALL RESPONSE")), null);
 		McpServerFeatures.SyncToolSpecification tool1 = McpServerFeatures.SyncToolSpecification.builder()
-			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(emptyJsonSchema).build())
+			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
 			.callHandler((exchange, request) -> {
 				// perform a blocking call to a remote service
 				try {
@@ -988,7 +980,7 @@ public abstract class AbstractMcpClientServerIntegrationTests {
 				.tool(Tool.builder()
 					.name("tool2")
 					.description("tool2 description")
-					.inputSchema(emptyJsonSchema)
+					.inputSchema(EMPTY_JSON_SCHEMA)
 					.build())
 				.callHandler((exchange, request) -> callResponse)
 				.build();
@@ -1040,7 +1032,7 @@ public abstract class AbstractMcpClientServerIntegrationTests {
 			.tool(Tool.builder()
 				.name("logging-test")
 				.description("Test logging notifications")
-				.inputSchema(emptyJsonSchema)
+				.inputSchema(EMPTY_JSON_SCHEMA)
 				.build())
 			.callHandler((exchange, request) -> {
 
@@ -1154,7 +1146,7 @@ public abstract class AbstractMcpClientServerIntegrationTests {
 			.tool(McpSchema.Tool.builder()
 				.name("progress-test")
 				.description("Test progress notifications")
-				.inputSchema(emptyJsonSchema)
+				.inputSchema(EMPTY_JSON_SCHEMA)
 				.build())
 			.callHandler((exchange, request) -> {
 
@@ -1308,7 +1300,7 @@ public abstract class AbstractMcpClientServerIntegrationTests {
 			.tool(Tool.builder()
 				.name("ping-async-test")
 				.description("Test ping async behavior")
-				.inputSchema(emptyJsonSchema)
+				.inputSchema(EMPTY_JSON_SCHEMA)
 				.build())
 			.callHandler((exchange, request) -> {
 

mcp-test/src/main/java/io/modelcontextprotocol/AbstractStatelessIntegrationTests.java

@@ -31,6 +31,7 @@ import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;
 import reactor.core.publisher.Mono;
 
+import static io.modelcontextprotocol.utils.ToolsUtils.EMPTY_JSON_SCHEMA;
 import static net.javacrumbs.jsonunit.assertj.JsonAssertions.assertThatJson;
 import static net.javacrumbs.jsonunit.assertj.JsonAssertions.json;
 import static org.assertj.core.api.Assertions.assertThat;
@@ -74,15 +75,6 @@ public abstract class AbstractStatelessIntegrationTests {
 	// ---------------------------------------
 	// Tools Tests
 	// ---------------------------------------
-
-	String emptyJsonSchema = """
-			{
-				"$schema": "http://json-schema.org/draft-07/schema#",
-				"type": "object",
-				"properties": {}
-			}
-			""";
-
 	@ParameterizedTest(name = "{0} : {displayName} ")
 	@ValueSource(strings = { "httpclient", "webflux" })
 	void testToolCallSuccess(String clientType) {
@@ -92,7 +84,7 @@ public abstract class AbstractStatelessIntegrationTests {
 		var callResponse = new McpSchema.CallToolResult(List.of(new McpSchema.TextContent("CALL RESPONSE")), null);
 		McpStatelessServerFeatures.SyncToolSpecification tool1 = McpStatelessServerFeatures.SyncToolSpecification
 			.builder()
-			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(emptyJsonSchema).build())
+			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
 			.callHandler((ctx, request) -> {
 
 				try {
@@ -145,7 +137,7 @@ public abstract class AbstractStatelessIntegrationTests {
 				.tool(Tool.builder()
 					.name("tool1")
 					.description("tool1 description")
-					.inputSchema(emptyJsonSchema)
+					.inputSchema(EMPTY_JSON_SCHEMA)
 					.build())
 				.callHandler((context, request) -> {
 					// We trigger a timeout on blocking read, raising an exception
@@ -180,7 +172,7 @@ public abstract class AbstractStatelessIntegrationTests {
 		var callResponse = new McpSchema.CallToolResult(List.of(new McpSchema.TextContent("CALL RESPONSE")), null);
 		McpStatelessServerFeatures.SyncToolSpecification tool1 = McpStatelessServerFeatures.SyncToolSpecification
 			.builder()
-			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(emptyJsonSchema).build())
+			.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(EMPTY_JSON_SCHEMA).build())
 			.callHandler((ctx, request) -> {
 				// perform a blocking call to a remote service
 				try {
@@ -241,7 +233,7 @@ public abstract class AbstractStatelessIntegrationTests {
 				.tool(Tool.builder()
 					.name("tool2")
 					.description("tool2 description")
-					.inputSchema(emptyJsonSchema)
+					.inputSchema(EMPTY_JSON_SCHEMA)
 					.build())
 				.callHandler((exchange, request) -> callResponse)
 				.build();

mcp-test/src/main/java/io/modelcontextprotocol/MockMcpTransport.java

@@ -9,8 +9,8 @@ import java.util.List;
 import java.util.function.BiConsumer;
 import java.util.function.Function;
 
-import com.fasterxml.jackson.core.type.TypeReference;
-import com.fasterxml.jackson.databind.ObjectMapper;
+import io.modelcontextprotocol.json.McpJsonMapper;
+import io.modelcontextprotocol.json.TypeRef;
 import io.modelcontextprotocol.spec.McpClientTransport;
 import io.modelcontextprotocol.spec.McpSchema;
 import io.modelcontextprotocol.spec.McpSchema.JSONRPCNotification;
@@ -93,8 +93,8 @@ public class MockMcpTransport implements McpClientTransport, McpServerTransport
 	}
 
 	@Override
-	public <T> T unmarshalFrom(Object data, TypeReference<T> typeRef) {
-		return new ObjectMapper().convertValue(data, typeRef);
+	public <T> T unmarshalFrom(Object data, TypeRef<T> typeRef) {
+		return McpJsonMapper.getDefault().convertValue(data, typeRef);
 	}
 
 }

mcp-test/src/main/java/io/modelcontextprotocol/client/AbstractMcpAsyncClientTests.java

@@ -4,6 +4,7 @@
 
 package io.modelcontextprotocol.client;
 
+import static io.modelcontextprotocol.utils.McpJsonMapperUtils.JSON_MAPPER;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatCode;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
@@ -22,8 +23,7 @@ import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Consumer;
 import java.util.function.Function;
 
-import org.junit.jupiter.api.AfterEach;
-import org.junit.jupiter.api.BeforeEach;
+import io.modelcontextprotocol.json.McpJsonMapper;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;
@@ -176,7 +176,12 @@ public abstract class AbstractMcpAsyncClientTests {
 				.consumeNextWith(result -> {
 					assertThat(result.tools()).isNotNull();
 					// Verify that the returned list is immutable
-					assertThatThrownBy(() -> result.tools().add(new Tool("test", "test", "{\"type\":\"object\"}")))
+					assertThatThrownBy(() -> result.tools()
+						.add(Tool.builder()
+							.name("test")
+							.title("test")
+							.inputSchema(JSON_MAPPER, "{\"type\":\"object\"}")
+							.build()))
 						.isInstanceOf(UnsupportedOperationException.class);
 				})
 				.verifyComplete();

mcp-test/src/main/java/io/modelcontextprotocol/client/AbstractMcpSyncClientTests.java

@@ -22,8 +22,6 @@ import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Consumer;
 import java.util.function.Function;
 
-import org.junit.jupiter.api.AfterEach;
-import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;

mcp-test/src/main/java/io/modelcontextprotocol/server/AbstractMcpAsyncServerTests.java

@@ -26,6 +26,7 @@ import org.junit.jupiter.params.provider.ValueSource;
 import reactor.core.publisher.Mono;
 import reactor.test.StepVerifier;
 
+import static io.modelcontextprotocol.utils.ToolsUtils.EMPTY_JSON_SCHEMA;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatCode;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
@@ -95,18 +96,10 @@ public abstract class AbstractMcpAsyncServerTests {
 	// ---------------------------------------
 	// Tools Tests
 	// ---------------------------------------
-	String emptyJsonSchema = """
-			{
-				"$schema": "http://json-schema.org/draft-07/schema#",
-				"type": "object",
-				"properties": {}
-			}
-			""";
-
 	@Test
 	@Deprecated
 	void testAddTool() {
-		Tool newTool = new McpSchema.Tool("new-tool", "New test tool", emptyJsonSchema);
+		Tool newTool = Tool.builder().name("new-tool").title("New test tool").inputSchema(EMPTY_JSON_SCHEMA).build();
 		var mcpAsyncServer = prepareAsyncServerBuilder().serverInfo("test-server", "1.0.0")
 			.capabilities(ServerCapabilities.builder().tools(true).build())
 			.build();
@@ -120,7 +113,7 @@ public abstract class AbstractMcpAsyncServerTests {
 
 	@Test
 	void testAddToolCall() {
-		Tool newTool = new McpSchema.Tool("new-tool", "New test tool", emptyJsonSchema);
+		Tool newTool = Tool.builder().name("new-tool").title("New test tool").inputSchema(EMPTY_JSON_SCHEMA).build();
 		var mcpAsyncServer = prepareAsyncServerBuilder().serverInfo("test-server", "1.0.0")
 			.capabilities(ServerCapabilities.builder().tools(true).build())
 			.build();
@@ -136,7 +129,11 @@ public abstract class AbstractMcpAsyncServerTests {
 	@Test
 	@Deprecated
 	void testAddDuplicateTool() {
-		Tool duplicateTool = new McpSchema.Tool(TEST_TOOL_NAME, "Duplicate tool", emptyJsonSchema);
+		Tool duplicateTool = McpSchema.Tool.builder()
+			.name(TEST_TOOL_NAME)
+			.title("Duplicate tool")
+			.inputSchema(EMPTY_JSON_SCHEMA)
+			.build();
 
 		var mcpAsyncServer = prepareAsyncServerBuilder().serverInfo("test-server", "1.0.0")
 			.capabilities(ServerCapabilities.builder().tools(true).build())
@@ -156,7 +153,11 @@ public abstract class AbstractMcpAsyncServerTests {
 
 	@Test
 	void testAddDuplicateToolCall() {
-		Tool duplicateTool = new McpSchema.Tool(TEST_TOOL_NAME, "Duplicate tool", emptyJsonSchema);
+		Tool duplicateTool = McpSchema.Tool.builder()
+			.name(TEST_TOOL_NAME)
+			.title("Duplicate tool")
+			.inputSchema(EMPTY_JSON_SCHEMA)
+			.build();
 
 		var mcpAsyncServer = prepareAsyncServerBuilder().serverInfo("test-server", "1.0.0")
 			.capabilities(ServerCapabilities.builder().tools(true).build())
@@ -176,8 +177,11 @@ public abstract class AbstractMcpAsyncServerTests {
 
 	@Test
 	void testDuplicateToolCallDuringBuilding() {
-		Tool duplicateTool = new Tool("duplicate-build-toolcall", "Duplicate toolcall during building",
-				emptyJsonSchema);
+		Tool duplicateTool = McpSchema.Tool.builder()
+			.name("duplicate-build-toolcall")
+			.title("Duplicate toolcall during building")
+			.inputSchema(EMPTY_JSON_SCHEMA)
+			.build();
 
 		assertThatThrownBy(() -> prepareAsyncServerBuilder().serverInfo("test-server", "1.0.0")
 			.capabilities(ServerCapabilities.builder().tools(true).build())
@@ -189,7 +193,11 @@ public abstract class AbstractMcpAsyncServerTests {
 
 	@Test
 	void testDuplicateToolsInBatchListRegistration() {
-		Tool duplicateTool = new Tool("batch-list-tool", "Duplicate tool in batch list", emptyJsonSchema);
+		Tool duplicateTool = McpSchema.Tool.builder()
+			.name("batch-list-tool")
+			.title("Duplicate tool in batch list")
+			.inputSchema(EMPTY_JSON_SCHEMA)
+			.build();
 		List<McpServerFeatures.AsyncToolSpecification> specs = List.of(
 				McpServerFeatures.AsyncToolSpecification.builder()
 					.tool(duplicateTool)
@@ -210,7 +218,11 @@ public abstract class AbstractMcpAsyncServerTests {
 
 	@Test
 	void testDuplicateToolsInBatchVarargsRegistration() {
-		Tool duplicateTool = new Tool("batch-varargs-tool", "Duplicate tool in batch varargs", emptyJsonSchema);
+		Tool duplicateTool = McpSchema.Tool.builder()
+			.name("batch-varargs-tool")
+			.title("Duplicate tool in batch varargs")
+			.inputSchema(EMPTY_JSON_SCHEMA)
+			.build();
 
 		assertThatThrownBy(() -> prepareAsyncServerBuilder().serverInfo("test-server", "1.0.0")
 			.capabilities(ServerCapabilities.builder().tools(true).build())
@@ -229,8 +241,11 @@ public abstract class AbstractMcpAsyncServerTests {
 
 	@Test
 	void testRemoveTool() {
-		Tool too = new McpSchema.Tool(TEST_TOOL_NAME, "Duplicate tool", emptyJsonSchema);
-
+		Tool too = McpSchema.Tool.builder()
+			.name(TEST_TOOL_NAME)
+			.title("Duplicate tool")
+			.inputSchema(EMPTY_JSON_SCHEMA)
+			.build();
 		var mcpAsyncServer = prepareAsyncServerBuilder().serverInfo("test-server", "1.0.0")
 			.capabilities(ServerCapabilities.builder().tools(true).build())
 			.toolCall(too, (exchange, request) -> Mono.just(new CallToolResult(List.of(), false)))
@@ -256,7 +271,11 @@ public abstract class AbstractMcpAsyncServerTests {
 
 	@Test
 	void testNotifyToolsListChanged() {
-		Tool too = new McpSchema.Tool(TEST_TOOL_NAME, "Duplicate tool", emptyJsonSchema);
+		Tool too = McpSchema.Tool.builder()
+			.name(TEST_TOOL_NAME)
+			.title("Duplicate tool")
+			.inputSchema(EMPTY_JSON_SCHEMA)
+			.build();
 
 		var mcpAsyncServer = prepareAsyncServerBuilder().serverInfo("test-server", "1.0.0")
 			.capabilities(ServerCapabilities.builder().tools(true).build())

mcp-test/src/main/java/io/modelcontextprotocol/server/AbstractMcpSyncServerTests.java

@@ -4,6 +4,7 @@
 
 package io.modelcontextprotocol.server;
 
+import static io.modelcontextprotocol.utils.ToolsUtils.EMPTY_JSON_SCHEMA;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatCode;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
@@ -99,15 +100,6 @@ public abstract class AbstractMcpSyncServerTests {
 	// ---------------------------------------
 	// Tools Tests
 	// ---------------------------------------
-
-	String emptyJsonSchema = """
-			{
-				"$schema": "http://json-schema.org/draft-07/schema#",
-				"type": "object",
-				"properties": {}
-			}
-			""";
-
 	@Test
 	@Deprecated
 	void testAddTool() {
@@ -115,7 +107,7 @@ public abstract class AbstractMcpSyncServerTests {
 			.capabilities(ServerCapabilities.builder().tools(true).build())
 			.build();
 
-		Tool newTool = new McpSchema.Tool("new-tool", "New test tool", emptyJsonSchema);
+		Tool newTool = Tool.builder().name("new-tool").title("New test tool").inputSchema(EMPTY_JSON_SCHEMA).build();
 		assertThatCode(() -> mcpSyncServer.addTool(new McpServerFeatures.SyncToolSpecification(newTool,
 				(exchange, args) -> new CallToolResult(List.of(), false))))
 			.doesNotThrowAnyException();
@@ -129,7 +121,7 @@ public abstract class AbstractMcpSyncServerTests {
 			.capabilities(ServerCapabilities.builder().tools(true).build())
 			.build();
 
-		Tool newTool = new McpSchema.Tool("new-tool", "New test tool", emptyJsonSchema);
+		Tool newTool = Tool.builder().name("new-tool").title("New test tool").inputSchema(EMPTY_JSON_SCHEMA).build();
 		assertThatCode(() -> mcpSyncServer.addTool(McpServerFeatures.SyncToolSpecification.builder()
 			.tool(newTool)
 			.callHandler((exchange, request) -> new CallToolResult(List.of(), false))
@@ -141,7 +133,11 @@ public abstract class AbstractMcpSyncServerTests {
 	@Test
 	@Deprecated
 	void testAddDuplicateTool() {
-		Tool duplicateTool = new McpSchema.Tool(TEST_TOOL_NAME, "Duplicate tool", emptyJsonSchema);
+		Tool duplicateTool = Tool.builder()
+			.name(TEST_TOOL_NAME)
+			.title("Duplicate tool")
+			.inputSchema(EMPTY_JSON_SCHEMA)
+			.build();
 
 		var mcpSyncServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
 			.capabilities(ServerCapabilities.builder().tools(true).build())
@@ -158,7 +154,11 @@ public abstract class AbstractMcpSyncServerTests {
 
 	@Test
 	void testAddDuplicateToolCall() {
-		Tool duplicateTool = new McpSchema.Tool(TEST_TOOL_NAME, "Duplicate tool", emptyJsonSchema);
+		Tool duplicateTool = Tool.builder()
+			.name(TEST_TOOL_NAME)
+			.title("Duplicate tool")
+			.inputSchema(EMPTY_JSON_SCHEMA)
+			.build();
 
 		var mcpSyncServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
 			.capabilities(ServerCapabilities.builder().tools(true).build())
@@ -176,8 +176,11 @@ public abstract class AbstractMcpSyncServerTests {
 
 	@Test
 	void testDuplicateToolCallDuringBuilding() {
-		Tool duplicateTool = new Tool("duplicate-build-toolcall", "Duplicate toolcall during building",
-				emptyJsonSchema);
+		Tool duplicateTool = Tool.builder()
+			.name("duplicate-build-toolcall")
+			.title("Duplicate toolcall during building")
+			.inputSchema(EMPTY_JSON_SCHEMA)
+			.build();
 
 		assertThatThrownBy(() -> prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
 			.capabilities(ServerCapabilities.builder().tools(true).build())
@@ -189,7 +192,11 @@ public abstract class AbstractMcpSyncServerTests {
 
 	@Test
 	void testDuplicateToolsInBatchListRegistration() {
-		Tool duplicateTool = new Tool("batch-list-tool", "Duplicate tool in batch list", emptyJsonSchema);
+		Tool duplicateTool = Tool.builder()
+			.name("batch-list-tool")
+			.title("Duplicate tool in batch list")
+			.inputSchema(EMPTY_JSON_SCHEMA)
+			.build();
 		List<McpServerFeatures.SyncToolSpecification> specs = List.of(
 				McpServerFeatures.SyncToolSpecification.builder()
 					.tool(duplicateTool)
@@ -210,7 +217,11 @@ public abstract class AbstractMcpSyncServerTests {
 
 	@Test
 	void testDuplicateToolsInBatchVarargsRegistration() {
-		Tool duplicateTool = new Tool("batch-varargs-tool", "Duplicate tool in batch varargs", emptyJsonSchema);
+		Tool duplicateTool = Tool.builder()
+			.name("batch-varargs-tool")
+			.title("Duplicate tool in batch varargs")
+			.inputSchema(EMPTY_JSON_SCHEMA)
+			.build();
 
 		assertThatThrownBy(() -> prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
 			.capabilities(ServerCapabilities.builder().tools(true).build())
@@ -229,7 +240,7 @@ public abstract class AbstractMcpSyncServerTests {
 
 	@Test
 	void testRemoveTool() {
-		Tool tool = new McpSchema.Tool(TEST_TOOL_NAME, "Test tool", emptyJsonSchema);
+		Tool tool = Tool.builder().name(TEST_TOOL_NAME).title("Test tool").inputSchema(EMPTY_JSON_SCHEMA).build();
 
 		var mcpSyncServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
 			.capabilities(ServerCapabilities.builder().tools(true).build())

mcp-test/src/main/java/io/modelcontextprotocol/utils/McpJsonMapperUtils.java

@@ -0,0 +1,12 @@
+package io.modelcontextprotocol.utils;
+
+import io.modelcontextprotocol.json.McpJsonMapper;
+
+public final class McpJsonMapperUtils {
+
+	private McpJsonMapperUtils() {
+	}
+
+	public static final McpJsonMapper JSON_MAPPER = McpJsonMapper.getDefault();
+
+}

mcp-test/src/main/java/io/modelcontextprotocol/utils/ToolsUtils.java

@@ -0,0 +1,15 @@
+package io.modelcontextprotocol.utils;
+
+import io.modelcontextprotocol.spec.McpSchema;
+
+import java.util.Collections;
+
+public final class ToolsUtils {
+
+	private ToolsUtils() {
+	}
+
+	public static final McpSchema.JsonSchema EMPTY_JSON_SCHEMA = new McpSchema.JsonSchema("object",
+			Collections.emptyMap(), null, null, null, null);
+
+}