Support runtime replacement in McpServer via put methods

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

@@ -137,6 +137,28 @@ void testAddDuplicateTool() {
 		assertThatCode(() -> mcpAsyncServer.closeGracefully().block(Duration.ofSeconds(10))).doesNotThrowAnyException();
 	}
 
+	@Test
+	void testPutTool() {
+		var mcpAsyncServer = McpServer.async(createMcpTransportProvider())
+			.serverInfo("test-server", "1.0.0")
+			.capabilities(ServerCapabilities.builder().tools(true).build())
+			.build();
+
+		Tool toolV1 = new McpSchema.Tool(TEST_TOOL_NAME, "Tool with version 1.0.0", emptyJsonSchema);
+
+		StepVerifier.create(mcpAsyncServer.putTool(new McpServerFeatures.AsyncToolSpecification(toolV1,
+				(exchange, args) -> Mono.just(new CallToolResult(List.of(), false)))))
+			.verifyComplete();
+
+		Tool toolV2 = new McpSchema.Tool(TEST_TOOL_NAME, "Tool with version 2.0.0", emptyJsonSchema);
+
+		StepVerifier.create(mcpAsyncServer.putTool(new McpServerFeatures.AsyncToolSpecification(toolV2,
+				(exchange, args) -> Mono.just(new CallToolResult(List.of(), false)))))
+			.verifyComplete();
+
+		assertThatCode(() -> mcpAsyncServer.closeGracefully().block(Duration.ofSeconds(10))).doesNotThrowAnyException();
+	}
+
 	@Test
 	void testRemoveTool() {
 		Tool too = new McpSchema.Tool(TEST_TOOL_NAME, "Duplicate tool", emptyJsonSchema);
@@ -201,7 +223,7 @@ void testAddResource() {
 			.capabilities(ServerCapabilities.builder().resources(true, false).build())
 			.build();
 
-		Resource resource = new Resource(TEST_RESOURCE_URI, "Test Resource", "text/plain", "Test resource description",
+		Resource resource = new Resource(TEST_RESOURCE_URI, "Test Resource", "Test resource description", "text/plain",
 				null);
 		McpServerFeatures.AsyncResourceSpecification specification = new McpServerFeatures.AsyncResourceSpecification(
 				resource, (exchange, req) -> Mono.just(new ReadResourceResult(List.of())));
@@ -233,7 +255,7 @@ void testAddResourceWithoutCapability() {
 			.serverInfo("test-server", "1.0.0")
 			.build();
 
-		Resource resource = new Resource(TEST_RESOURCE_URI, "Test Resource", "text/plain", "Test resource description",
+		Resource resource = new Resource(TEST_RESOURCE_URI, "Test Resource", "Test resource description", "text/plain",
 				null);
 		McpServerFeatures.AsyncResourceSpecification specification = new McpServerFeatures.AsyncResourceSpecification(
 				resource, (exchange, req) -> Mono.just(new ReadResourceResult(List.of())));
@@ -244,6 +266,28 @@ void testAddResourceWithoutCapability() {
 		});
 	}
 
+	@Test
+	void testPutResource() {
+		var mcpAsyncServer = McpServer.async(createMcpTransportProvider())
+			.serverInfo("test-server", "1.0.0")
+			.capabilities(ServerCapabilities.builder().resources(true, false).build())
+			.build();
+
+		Resource resourceV1 = new Resource(TEST_RESOURCE_URI, "Test Resource", "Resource with version 1.0.0",
+				"text/plain", null);
+		McpServerFeatures.AsyncResourceSpecification specificationV1 = new McpServerFeatures.AsyncResourceSpecification(
+				resourceV1, (exchange, req) -> Mono.just(new ReadResourceResult(List.of())));
+		StepVerifier.create(mcpAsyncServer.putResource(specificationV1)).verifyComplete();
+
+		Resource resourceV2 = new Resource(TEST_RESOURCE_URI, "Test Resource", "Resource with version 2.0.0",
+				"text/plain", null);
+		McpServerFeatures.AsyncResourceSpecification specificationV2 = new McpServerFeatures.AsyncResourceSpecification(
+				resourceV2, (exchange, req) -> Mono.just(new ReadResourceResult(List.of())));
+		StepVerifier.create(mcpAsyncServer.putResource(specificationV2)).verifyComplete();
+
+		assertThatCode(() -> mcpAsyncServer.closeGracefully().block(Duration.ofSeconds(10))).doesNotThrowAnyException();
+	}
+
 	@Test
 	void testRemoveResourceWithoutCapability() {
 		// Create a server without resource capabilities
@@ -301,6 +345,28 @@ void testAddPromptWithoutCapability() {
 		});
 	}
 
+	@Test
+	void testPutPrompt() {
+		var mcpAsyncServer = McpServer.async(createMcpTransportProvider())
+			.serverInfo("test-server", "1.0.0")
+			.capabilities(ServerCapabilities.builder().prompts(false).build())
+			.build();
+
+		Prompt promptV1 = new Prompt(TEST_PROMPT_NAME, "Prompt with version 1.0.0", List.of());
+		McpServerFeatures.AsyncPromptSpecification specificationV1 = new McpServerFeatures.AsyncPromptSpecification(
+				promptV1, (exchange, req) -> Mono.just(new GetPromptResult("Test prompt description", List
+					.of(new PromptMessage(McpSchema.Role.ASSISTANT, new McpSchema.TextContent("Test content"))))));
+
+		StepVerifier.create(mcpAsyncServer.putPrompt(specificationV1)).verifyComplete();
+
+		Prompt promptV2 = new Prompt(TEST_PROMPT_NAME, "Prompt with version 2.0.0", List.of());
+		McpServerFeatures.AsyncPromptSpecification specificationV2 = new McpServerFeatures.AsyncPromptSpecification(
+				promptV2, (exchange, req) -> Mono.just(new GetPromptResult("Test prompt description", List
+					.of(new PromptMessage(McpSchema.Role.ASSISTANT, new McpSchema.TextContent("Test content"))))));
+
+		StepVerifier.create(mcpAsyncServer.putPrompt(specificationV2)).verifyComplete();
+	}
+
 	@Test
 	void testRemovePromptWithoutCapability() {
 		// Create a server without prompt capabilities

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

@@ -141,6 +141,28 @@ void testAddDuplicateTool() {
 		assertThatCode(() -> mcpSyncServer.closeGracefully()).doesNotThrowAnyException();
 	}
 
+	@Test
+	void testPutTool() {
+		var mcpSyncServer = McpServer.sync(createMcpTransportProvider())
+			.serverInfo("test-server", "1.0.0")
+			.capabilities(ServerCapabilities.builder().tools(true).build())
+			.build();
+
+		Tool toolV1 = new McpSchema.Tool(TEST_TOOL_NAME, "Tool with version 1.0.0", emptyJsonSchema);
+
+		assertThatCode(() -> mcpSyncServer.putTool(new McpServerFeatures.SyncToolSpecification(toolV1,
+				(exchange, args) -> new CallToolResult(List.of(), false))))
+			.doesNotThrowAnyException();
+
+		Tool toolV2 = new McpSchema.Tool(TEST_TOOL_NAME, "Tool with version 2.0.0", emptyJsonSchema);
+
+		assertThatCode(() -> mcpSyncServer.putTool(new McpServerFeatures.SyncToolSpecification(toolV2,
+				(exchange, args) -> new CallToolResult(List.of(), false))))
+			.doesNotThrowAnyException();
+
+		assertThatCode(() -> mcpSyncServer.closeGracefully()).doesNotThrowAnyException();
+	}
+
 	@Test
 	void testRemoveTool() {
 		Tool tool = new McpSchema.Tool(TEST_TOOL_NAME, "Test tool", emptyJsonSchema);
@@ -198,7 +220,7 @@ void testAddResource() {
 			.capabilities(ServerCapabilities.builder().resources(true, false).build())
 			.build();
 
-		Resource resource = new Resource(TEST_RESOURCE_URI, "Test Resource", "text/plain", "Test resource description",
+		Resource resource = new Resource(TEST_RESOURCE_URI, "Test Resource", "Test resource description", "text/plain",
 				null);
 		McpServerFeatures.SyncResourceSpecification specification = new McpServerFeatures.SyncResourceSpecification(
 				resource, (exchange, req) -> new ReadResourceResult(List.of()));
@@ -228,7 +250,7 @@ void testAddResourceWithoutCapability() {
 			.serverInfo("test-server", "1.0.0")
 			.build();
 
-		Resource resource = new Resource(TEST_RESOURCE_URI, "Test Resource", "text/plain", "Test resource description",
+		Resource resource = new Resource(TEST_RESOURCE_URI, "Test Resource", "Test resource description", "text/plain",
 				null);
 		McpServerFeatures.SyncResourceSpecification specification = new McpServerFeatures.SyncResourceSpecification(
 				resource, (exchange, req) -> new ReadResourceResult(List.of()));
@@ -237,6 +259,28 @@ void testAddResourceWithoutCapability() {
 			.hasMessage("Server must be configured with resource capabilities");
 	}
 
+	@Test
+	void testPutResource() {
+		var mcpSyncServer = McpServer.sync(createMcpTransportProvider())
+			.serverInfo("test-server", "1.0.0")
+			.capabilities(ServerCapabilities.builder().resources(true, false).build())
+			.build();
+
+		Resource resourceV1 = new Resource(TEST_RESOURCE_URI, "Test Resource", "Resource with version 1.0.0",
+				"text/plain", null);
+		McpServerFeatures.SyncResourceSpecification specificationV1 = new McpServerFeatures.SyncResourceSpecification(
+				resourceV1, (exchange, req) -> new ReadResourceResult(List.of()));
+		assertThatCode(() -> mcpSyncServer.putResource(specificationV1)).doesNotThrowAnyException();
+
+		Resource resourceV2 = new Resource(TEST_RESOURCE_URI, "Test Resource", "Resource with version 2.0.0",
+				"text/plain", null);
+		McpServerFeatures.SyncResourceSpecification specificationV2 = new McpServerFeatures.SyncResourceSpecification(
+				resourceV2, (exchange, req) -> new ReadResourceResult(List.of()));
+		assertThatCode(() -> mcpSyncServer.putResource(specificationV2)).doesNotThrowAnyException();
+
+		assertThatCode(() -> mcpSyncServer.closeGracefully()).doesNotThrowAnyException();
+	}
+
 	@Test
 	void testRemoveResourceWithoutCapability() {
 		var serverWithoutResources = McpServer.sync(createMcpTransportProvider())
@@ -287,6 +331,26 @@ void testAddPromptWithoutCapability() {
 			.hasMessage("Server must be configured with prompt capabilities");
 	}
 
+	@Test
+	void testPutPrompt() {
+		var mcpSyncServer = McpServer.sync(createMcpTransportProvider())
+			.serverInfo("test-server", "1.0.0")
+			.capabilities(ServerCapabilities.builder().prompts(false).build())
+			.build();
+
+		Prompt promptV1 = new Prompt(TEST_PROMPT_NAME, "Prompt with version 1.0.0", List.of());
+		McpServerFeatures.SyncPromptSpecification specificationV1 = new McpServerFeatures.SyncPromptSpecification(
+				promptV1, (exchange, req) -> new GetPromptResult("Test prompt description", List
+					.of(new PromptMessage(McpSchema.Role.ASSISTANT, new McpSchema.TextContent("Test content")))));
+		assertThatCode(() -> mcpSyncServer.putPrompt(specificationV1)).doesNotThrowAnyException();
+
+		Prompt promptV2 = new Prompt(TEST_PROMPT_NAME, "Prompt with version 2.0.0", List.of());
+		McpServerFeatures.SyncPromptSpecification specificationV2 = new McpServerFeatures.SyncPromptSpecification(
+				promptV2, (exchange, req) -> new GetPromptResult("Test prompt description", List
+					.of(new PromptMessage(McpSchema.Role.ASSISTANT, new McpSchema.TextContent("Test content")))));
+		assertThatCode(() -> mcpSyncServer.putPrompt(specificationV2)).doesNotThrowAnyException();
+	}
+
 	@Test
 	void testRemovePromptWithoutCapability() {
 		var serverWithoutPrompts = McpServer.sync(createMcpTransportProvider())

mcp/src/main/java/io/modelcontextprotocol/server/McpAsyncServer.java

@@ -303,6 +303,44 @@ public Mono<Void> addTool(McpServerFeatures.AsyncToolSpecification toolSpecifica
 		});
 	}
 
+	/**
+	 * Replaces an existing tool handler or adds a new one if it doesn't exist.
+	 * @param toolSpecification The tool specification to put
+	 * @return Mono that completes when clients have been notified of the change
+	 */
+	public Mono<Void> putTool(McpServerFeatures.AsyncToolSpecification toolSpecification) {
+		if (toolSpecification == null) {
+			return Mono.error(new McpError("Tool specification must not be null"));
+		}
+		if (toolSpecification.tool() == null) {
+			return Mono.error(new McpError("Tool must not be null"));
+		}
+		if (toolSpecification.call() == null) {
+			return Mono.error(new McpError("Tool call handler must not be null"));
+		}
+		if (this.serverCapabilities.tools() == null) {
+			return Mono.error(new McpError("Server must be configured with tool capabilities"));
+		}
+
+		return Mono.defer(() -> {
+			this.tools.replaceAll(asyncToolSpecification -> {
+				if (!asyncToolSpecification.tool().name().equals(toolSpecification.tool().name())) {
+					return asyncToolSpecification;
+				}
+				logger.debug("Replaced tool handler: {}", toolSpecification.tool().name());
+				return toolSpecification;
+			});
+			if (this.tools.addIfAbsent(toolSpecification)) {
+				logger.debug("Added tool handler: {}", toolSpecification.tool().name());
+			}
+
+			if (this.serverCapabilities.tools().listChanged()) {
+				return notifyToolsListChanged();
+			}
+			return Mono.empty();
+		});
+	}
+
 	/**
 	 * Remove a tool handler at runtime.
 	 * @param toolName The name of the tool handler to remove
@@ -396,6 +434,34 @@ public Mono<Void> addResource(McpServerFeatures.AsyncResourceSpecification resou
 		});
 	}
 
+	/**
+	 * Replaces an existing resource handler or adds a new one if it doesn't exist.
+	 * @param resourceSpecification The resource handler to put
+	 * @return Mono that completes when clients have been notified of the change
+	 */
+	public Mono<Void> putResource(McpServerFeatures.AsyncResourceSpecification resourceSpecification) {
+		if (resourceSpecification == null || resourceSpecification.resource() == null) {
+			return Mono.error(new McpError("Resource must not be null"));
+		}
+
+		if (this.serverCapabilities.resources() == null) {
+			return Mono.error(new McpError("Server must be configured with resource capabilities"));
+		}
+
+		return Mono.defer(() -> {
+			if (this.resources.put(resourceSpecification.resource().uri(), resourceSpecification) != null) {
+				logger.debug("Replaced resource handler: {}", resourceSpecification.resource().uri());
+			}
+			else {
+				logger.debug("Added resource handler: {}", resourceSpecification.resource().uri());
+			}
+			if (this.serverCapabilities.resources().listChanged()) {
+				return notifyResourcesListChanged();
+			}
+			return Mono.empty();
+		});
+	}
+
 	/**
 	 * Remove a resource handler at runtime.
 	 * @param resourceUri The URI of the resource handler to remove
@@ -520,6 +586,36 @@ public Mono<Void> addPrompt(McpServerFeatures.AsyncPromptSpecification promptSpe
 		});
 	}
 
+	/**
+	 * Replaces an existing prompt handler or adds a new one if it doesn't exist.
+	 * @param promptSpecification The prompt handler to put
+	 * @return Mono that completes when clients have been notified of the change
+	 */
+	public Mono<Void> putPrompt(McpServerFeatures.AsyncPromptSpecification promptSpecification) {
+		if (promptSpecification == null) {
+			return Mono.error(new McpError("Prompt specification must not be null"));
+		}
+		if (this.serverCapabilities.prompts() == null) {
+			return Mono.error(new McpError("Server must be configured with prompt capabilities"));
+		}
+
+		return Mono.defer(() -> {
+			if (this.prompts.put(promptSpecification.prompt().name(), promptSpecification) != null) {
+				logger.debug("Replaced prompt handler: {}", promptSpecification.prompt().name());
+			}
+			else {
+				logger.debug("Added prompt handler: {}", promptSpecification.prompt().name());
+			}
+
+			// Servers that declared the listChanged capability SHOULD send a
+			// notification, when the list of available prompts changes
+			if (this.serverCapabilities.prompts().listChanged()) {
+				return notifyPromptsListChanged();
+			}
+			return Mono.empty();
+		});
+	}
+
 	/**
 	 * Remove a prompt handler at runtime.
 	 * @param promptName The name of the prompt handler to remove

mcp/src/main/java/io/modelcontextprotocol/server/McpSyncServer.java

@@ -71,6 +71,14 @@ public void addTool(McpServerFeatures.SyncToolSpecification toolHandler) {
 		this.asyncServer.addTool(McpServerFeatures.AsyncToolSpecification.fromSync(toolHandler)).block();
 	}
 
+	/**
+	 * Put a new tool handler or update an existing one.
+	 * @param toolHandler The tool handler to put
+	 */
+	public void putTool(McpServerFeatures.SyncToolSpecification toolHandler) {
+		this.asyncServer.putTool(McpServerFeatures.AsyncToolSpecification.fromSync(toolHandler)).block();
+	}
+
 	/**
 	 * Remove a tool handler.
 	 * @param toolName The name of the tool handler to remove
@@ -87,6 +95,14 @@ public void addResource(McpServerFeatures.SyncResourceSpecification resourceHand
 		this.asyncServer.addResource(McpServerFeatures.AsyncResourceSpecification.fromSync(resourceHandler)).block();
 	}
 
+	/**
+	 * Put a new resource handler or update an existing one.
+	 * @param resourceHandler The resource handler to put
+	 */
+	public void putResource(McpServerFeatures.SyncResourceSpecification resourceHandler) {
+		this.asyncServer.putResource(McpServerFeatures.AsyncResourceSpecification.fromSync(resourceHandler)).block();
+	}
+
 	/**
 	 * Remove a resource handler.
 	 * @param resourceUri The URI of the resource handler to remove
@@ -103,6 +119,14 @@ public void addPrompt(McpServerFeatures.SyncPromptSpecification promptSpecificat
 		this.asyncServer.addPrompt(McpServerFeatures.AsyncPromptSpecification.fromSync(promptSpecification)).block();
 	}
 
+	/**
+	 * Put a new prompt handler or update an existing one.
+	 * @param promptSpecification The prompt specification to put
+	 */
+	public void putPrompt(McpServerFeatures.SyncPromptSpecification promptSpecification) {
+		this.asyncServer.putPrompt(McpServerFeatures.AsyncPromptSpecification.fromSync(promptSpecification)).block();
+	}
+
 	/**
 	 * Remove a prompt handler.
 	 * @param promptName The name of the prompt handler to remove