fastify-mcp

- Integrates MCP servers into any Fastify application.
- Supports Streamable HTTP and legacy HTTP+SSE transports.
- Built‑in session management with event emitters (connected, terminated, error).
- Works with the official MCP TypeScript SDK.
- Configurable endpoint path and stateful/stateless modes.

First, define your MCP server.

function createServer() {
  const mcpServer = new McpServer({
    name: "...",
    version: "...",
  });
mcpServer.tool("...");

  mcpServer.resource("...");
return mcpServer.server;

}

Create a Fastify app and register the plugin.

import { fastify } from "fastify";
import { streamableHttp } from "fastify-mcp";
import { StreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/streamableHttp.js";
const app = fastify();
app.register(streamableHttp, {

  // Set to true if you want a stateful server

  stateful: false,

  mcpEndpoint: "/mcp",

  sessions: new Sessions<StreamableHTTPServerTransport>()

  createServer,

});
app.listen({ port: 8080 });

See the examples directory for more detailed examples.