MCP（Model Context Protocol）実践ガイド — AIエージェントと外部ツールをつなぐ新標準の導入から自作サーバー構築まで

{
  "mcpServers": {
    "filesystem": {
      "command": "npx",
      "args": [
        "-y",
        "@modelcontextprotocol/server-filesystem",
        "/Users/username/Projects"
      ]
    }
  }
}

{
  "mcpServers": {
    "github": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-github"],
      "env": {
        "GITHUB_PERSONAL_ACCESS_TOKEN": "ghp_xxxxx"
      }
    }
  }
}

claude mcp add github -e GITHUB_PERSONAL_ACCESS_TOKEN=ghp_xxxxx -- npx -y @modelcontextprotocol/server-github

mkdir my-mcp-server && cd my-mcp-server
npm init -y
npm install @modelcontextprotocol/sdk zod
npm install -D typescript @types/node
npx tsc --init --module nodenext --moduleResolution nodenext --outDir dist

{
  "type": "module",
  "bin": { "my-mcp-server": "dist/index.js" },
  "scripts": {
    "build": "tsc",
    "start": "node dist/index.js"
  }
}

#!/usr/bin/env node
import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
import { z } from "zod";

// インメモリのTODOストア
interface Todo {
  id: number;
  title: string;
  done: boolean;
}
let todos: Todo[] = [];
let nextId = 1;

const server = new McpServer({
  name: "todo-manager",
  version: "1.0.0",
});

// --- Tool: TODOを追加 ---
server.tool(
  "add_todo",
  "新しいTODOを追加する",
  { title: z.string().describe("TODOのタイトル") },
  async ({ title }) => {
    const todo: Todo = { id: nextId++, title, done: false };
    todos.push(todo);
    return {
      content: [
        { type: "text", text: `TODO #${todo.id} "${todo.title}" を追加しました` },
      ],
    };
  }
);

// --- Tool: TODOを完了にする ---
server.tool(
  "complete_todo",
  "指定IDのTODOを完了にする",
  { id: z.number().describe("TODOのID") },
  async ({ id }) => {
    const todo = todos.find((t) => t.id === id);
    if (!todo) {
      return { content: [{ type: "text", text: `ID ${id} のTODOが見つかりません` }] };
    }
    todo.done = true;
    return {
      content: [{ type: "text", text: `TODO #${id} "${todo.title}" を完了にしました` }],
    };
  }
);

// --- Resource: TODO一覧 ---
server.resource(
  "todo_list",
  "todo://list",
  { description: "現在のTODO一覧を取得する" },
  async () => ({
    contents: [
      {
        uri: "todo://list",
        mimeType: "application/json",
        text: JSON.stringify(todos, null, 2),
      },
    ],
  })
);

// --- 起動 ---
const transport = new StdioServerTransport();
await server.connect(transport);

npm run build

{
  "mcpServers": {
    "todo-manager": {
      "command": "node",
      "args": ["/path/to/my-mcp-server/dist/index.js"]
    }
  }
}

// NG: 通信が壊れる
console.log("debug info");

// OK: stderrに出す
console.error("debug info");

npx -y @modelcontextprotocol/server-filesystem@latest

import express from "express";
import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { StreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/streamableHttp.js";

const app = express();
app.use(express.json());

const server = new McpServer({ name: "remote-todo", version: "1.0.0" });
// ... tool/resource登録は同じ ...

app.post("/mcp", async (req, res) => {
  const transport = new StreamableHTTPServerTransport({
    sessionIdGenerator: undefined,
  });
  res.on("close", () => transport.close());
  await server.connect(transport);
  await transport.handleRequest(req, res);
});

app.listen(8080, () => {
  console.error("MCP server listening on http://localhost:8080/mcp");
});