How to Build an MCP Server in Java

<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>io.modelcontextprotocol.sdk</groupId>
      <artifactId>mcp-bom</artifactId>
      <version>2.1.0</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
  </dependencies>
</dependencyManagement>

<dependencies>
  <dependency>
    <groupId>io.modelcontextprotocol.sdk</groupId>
    <artifactId>mcp</artifactId>
  </dependency>
</dependencies>

import io.modelcontextprotocol.json.McpJsonDefaults;
import io.modelcontextprotocol.server.McpServer;
import io.modelcontextprotocol.server.transport.StdioServerTransportProvider;
import io.modelcontextprotocol.spec.McpSchema;
import io.modelcontextprotocol.spec.McpSchema.CallToolResult;
import io.modelcontextprotocol.spec.McpSchema.ServerCapabilities;
import io.modelcontextprotocol.spec.McpSchema.Tool;

import java.util.List;
import java.util.Map;

public class EchoServer {

    public static void main(String[] args) {
        var transportProvider =
            new StdioServerTransportProvider(McpJsonDefaults.getMapper());

        Map<String, Object> schema = Map.of(
            "type", "object",
            "properties", Map.of("text", Map.of("type", "string")),
            "required", List.of("text"));

        McpServer.sync(transportProvider)
            .serverInfo("echo-server", "1.0.0")
            .capabilities(ServerCapabilities.builder().tools(true).build())
            .toolCall(
                Tool.builder("echo", schema).description("Echoes input").build(),
                (exchange, request) -> CallToolResult.builder()
                    .content(List.of(new McpSchema.TextContent(
                        request.arguments().get("text").toString())))
                    .build())
            .build();
    }
}

# Test in MCP Inspector
npx @modelcontextprotocol/inspector java -jar /absolute/path/to/echo-server.jar

# Claude Code (everything after -- is the launch command)
claude mcp add echo -- java -jar /absolute/path/to/echo-server.jar

{
  "mcpServers": {
    "echo": {
      "command": "java",
      "args": ["-jar", "/absolute/path/to/echo-server.jar"]
    }
  }
}

@SpringBootApplication
public class McpServerApplication {
    public static void main(String[] args) {
        SpringApplication.run(McpServerApplication.class, args);
    }

    @Bean
    public ToolCallbackProvider weatherTools(WeatherService weatherService) {
        return MethodToolCallbackProvider.builder().toolObjects(weatherService).build();
    }
}

// In your service class, annotate each tool method:
// @Tool(description = "Get weather alerts for a US state")
// public String getAlerts(@ToolParam(description = "Two-letter US state code") String state) { ... }