Fastify MCP Server

What is fastify-mcp?

fastify-mcp integrates Model Context Protocol (MCP) servers with your Fastify application. It supports both the Streamable HTTP transport and the legacy HTTP+SSE transport, and is designed for developers building MCP-compatible tools and resources on top of Fastify.

How to use fastify-mcp?

Install with npm install fastify-mcp or yarn add fastify-mcp. Define an MCP server using McpServer from the MCP TypeScript SDK, then register the streamableHttp plugin on a Fastify app, passing options such as stateful, mcpEndpoint, sessions, and createServer. The plugin handles session management automatically using an in-memory mapping.

Key features of 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.

Use cases of fastify-mcp

• Expose MCP tools and resources through a Fastify web server.
• Build stateful MCP servers that manage multiple client sessions.
• Add MCP endpoints to existing Fastify applications with minimal overhead.
• Leverage Fastify’s plugin ecosystem for logging, authentication, and routing.