Fast MCP Server

Overview

FastMCP is a TypeScript framework that makes it easy to build Model Context Protocol (MCP) servers. It provides a clean, type-safe API for defining tools that can be used by AI models to interact with your application.

Installation

You can install FastMCP using npm, yarn, or pnpm:

npm install fastmcp
# or
yarn add fastmcp
# or
pnpm add fastmcp

Basic Usage

Creating a simple MCP server with FastMCP is straightforward:

import { FastMCP } from "fastmcp";
import { z } from "zod"; // Or any validation library that supports Standard Schema

const server = new FastMCP({
  name: "My Server",
  version: "1.0.0",
});

server.addTool({
  name: "add",
  description: "Add two numbers",
  parameters: z.object({
    a: z.number(),
    b: z.number(),
  }),
  execute: async (args) => {
    return String(args.a + args.b);
  },
});

server.start({
  transportType: "stdio",
});

Transport Options

FastMCP supports multiple transport types:

1. stdio - For local development and testing
2. SSE (Server-Sent Events) - For remote communication over HTTP
3. HTTP Streaming - For more efficient remote communication

Setting up SSE transport:

server.start({
  transportType: "sse",
  sse: {
    endpoint: "/sse",
    port: 8080,
  },
});

Setting up HTTP Streaming:

server.start({
  transportType: "httpStream",
  httpStream: {
    endpoint: "/stream",
    port: 8080,
  },
});

Advanced Features

FastMCP includes many advanced features:

• Authentication: Secure your MCP server with custom authentication logic
• Sessions: Maintain state across multiple client interactions
• Content Types: Return images, audio, and other content types
• Logging: Comprehensive logging for debugging
• Error Handling: Graceful error handling and reporting
• Progress Notifications: Provide feedback during long-running operations
• Typed Server Events: Type-safe server event handling
• Prompt Argument Auto-completion: Improve developer experience

Testing and Debugging

FastMCP provides CLI tools for testing and debugging your MCP servers:

# Test a server using CLI
npx fastmcp dev path/to/server.ts

# Debug a server using MCP Inspector
npx fastmcp inspect path/to/server.ts

Schema Validation

FastMCP supports multiple schema validation libraries through the Standard Schema specification:

• Zod
• ArkType
• Valibot

Choose the one that best fits your project's needs.