java-sdk/mcp-spring/mcp-spring-webflux
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Filename Latest commit message Latest commit date
Christian Tzolov 8a2f97f1b1 feat: add structured output support for MCP tools (#357)
- Add JsonSchemaValidator interface and DefaultJsonSchemaValidator implementation
 - put the JsonSchemaValidator classes into a dedicated spec package
 - add schema caching to DefaultJsonSchemaValidator for better performance
- Extend Tool schema to support outputSchema field for defining expected output structure
- Add structuredContent field to CallToolResult for validated structured responses
- Implement automatic validation of tool outputs against their defined schemas
- Add comprehensive test coverage for structured output validation scenarios
- Add json-schema-validator and json-unit-assertj dependencies for validation and testing
- Update McpServer builders to accept custom JsonSchemaValidator instances
- Ensure backward compatibility with existing tools without output schemas

This implements the MCP specification requirement that tools with output schemas
must provide structured results conforming to those schemas, with automatic
validation and error handling for non-conforming outputs.
https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content

Signed-off-by: Christian Tzolov <christian.tzolov@broadcom.com>
2025-07-13 15:29:56 +02:00
..
src feat: add structured output support for MCP tools (#357) 2025-07-13 15:29:56 +02:00
pom.xml feat: add structured output support for MCP tools (#357) 2025-07-13 15:29:56 +02:00
README.md Module and Package restructoring 2025-01-29 13:40:53 +01:00

WebFlux SSE Transport

<dependency>
    <groupId>io.modelcontextprotocol.sdk</groupId>
    <artifactId>mcp-spring-webflux</artifactId>
</dependency>
String MESSAGE_ENDPOINT = "/mcp/message";

@Configuration
static class MyConfig {

    // SSE transport
	@Bean
	public WebFluxSseServerTransport sseServerTransport() {
		return new WebFluxSseServerTransport(new ObjectMapper(), "/mcp/message");
	}

	// Router function for SSE transport used by Spring WebFlux to start an HTTP
	// server.
	@Bean
	public RouterFunction<?> mcpRouterFunction(WebFluxSseServerTransport transport) {
		return transport.getRouterFunction();
	}

	@Bean
	public McpAsyncServer mcpServer(ServerMcpTransport transport, OpenLibrary openLibrary) {

		// Configure server capabilities with resource support
		var capabilities = McpSchema.ServerCapabilities.builder()
			.resources(false, true) // No subscribe support, but list changes notifications
			.tools(true) // Tool support with list changes notifications
			.prompts(true) // Prompt support with list changes notifications
			.logging() // Logging support
			.build();

		// Create the server with both tool and resource capabilities
		var server = McpServer.using(transport)
			.serverInfo("MCP Demo Server", "1.0.0")
			.capabilities(capabilities)
			.resources(systemInfoResourceRegistration())
			.prompts(greetingPromptRegistration())
			.tools(openLibraryToolRegistrations(openLibrary))
			.async();
		
		return server;
	} 

    // ...

}