fastmcp

FastMCP Development Skill

FastMCP is a TypeScript framework for building Model Context Protocol (MCP) servers. This skill provides patterns for tools, resources, prompts, authentication, and transport configuration.

Installation

npm install fastmcp

Basic Server Setup

import { FastMCP } from "fastmcp";
import { z } from "zod";

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

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

Tools

Basic Tool with Zod Schema

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);
  },
});

Tool Without Parameters

server.addTool({
  name: "sayHello",
  description: "Say hello",
  execute: async () => {
    return "Hello, world!";
  },
});

Tool with Logging

server.addTool({
  name: "download",
  parameters: z.object({ url: z.string() }),
  execute: async (args, { log }) => {
    log.info("Downloading file...", { url: args.url });
    // ... process ...
    log.info("Downloaded file");
    return "done";
  },
});

Tool with Progress Reporting

server.addTool({
  name: "download",
  execute: async (args, { reportProgress }) => {
    await reportProgress({ progress: 0, total: 100 });
    // ... process ...
    await reportProgress({ progress: 100, total: 100 });
    return "done";
  },
});

Tool with Streaming Output

server.addTool({
  name: "generateText",
  parameters: z.object({ prompt: z.string() }),
  annotations: {
    streamingHint: true,
    readOnlyHint: true,
  },
  execute: async (args, { streamContent }) => {
    await streamContent({ type: "text", text: "Starting...\n" });
    const words = "The quick brown fox".split(" ");
    for (const word of words) {
      await streamContent({ type: "text", text: word + " " });
      await new Promise(resolve => setTimeout(resolve, 300));
    }
    return;
  },
});