Java MCP SDK: Complete Developer Guide

Overview

The Java MCP SDK is the official library for building MCP servers in Java. It supports tools, resources, prompts, transports, and the stdio and streamable-http transport.

Installation

implementation 'io.modelcontextprotocol:sdk'

Minimal Server Example

@SpringBootApplication
public class MyMcpServer {
    @Bean
    public McpServerFeatures.SyncToolSpecification addTool() {
        return new McpServerFeatures.SyncToolSpecification(
            new Tool("add", "Add two numbers",
                Map.of("a", Map.of("type", "integer"),
                       "b", Map.of("type", "integer"))),
            (exchange, args) -> new CallToolResult(
                String.valueOf((int)args.get("a") + (int)args.get("b")))
        );
    }
}

Adding a Tool

Tools are the primary way MCP servers expose functionality to clients. Each tool has a name, input schema, and handler function.

// Register additional tools as Spring @Bean methods

Supported Features

Testing Your Server

1. Start the server and verify it prints no startup errors.
2. Run npx @modelcontextprotocol/inspector and connect over stdio.
3. Call your tools and verify they return the expected responses.
4. Connect from Claude Desktop and confirm tool visibility.