MCP TypeScript SDK

::: info v2 beta This is the documentation for v2 of the SDK, currently in beta: the API is settling but can still change before the stable release alongside the 2026-07-28 spec. Tell us what you find — and if you need the stable v1, its documentation is at ts.sdk.modelcontextprotocol.io. :::

The Model Context Protocol (MCP) is an open standard that connects AI applications to the systems where your data and tools live. You write a server that exposes tools, resources, and prompts; any MCP host — Claude Code, VS Code, Cursor, your own application — connects to it and lets a model use them. The protocol is defined by the MCP specification; this SDK is its TypeScript implementation, on Node.js, Bun, and Deno.

A complete server is one file:

import { McpServer } from '@modelcontextprotocol/server';
import { serveStdio } from '@modelcontextprotocol/server/stdio';
import * as z from 'zod/v4';

serveStdio(() => {
    const server = new McpServer({ name: 'weather', version: '1.0.0' });

    server.registerTool(
        'get-forecast',
        {
            description: 'Get the weather forecast for a city',
            inputSchema: z.object({ city: z.string() })
        },
        async ({ city }) => ({
            content: [{ type: 'text', text: `Sunny in ${city} all week.` }]
        })
    );

    return server;
});

Any MCP host that launches this program lists and calls get-forecast; the SDK validates every call against that z.object(...) schema before your handler runs. Build a server installs the packages and runs it end to end.

Pick a path

• Expose your API or data to AI applications → Build a server
• Build an application that talks to MCP servers → Build a client
• Coming from v1 (@modelcontextprotocol/sdk) → Upgrade
• Drop MCP into the app you already run → Express · Hono · Fastify · Workers

For exact signatures, go to the API reference.

Recap

• MCP connects AI applications to the systems where your tools and data live; you build one side, a host brings the model.
• registerTool(name, config, handler) with a z.object(...) inputSchema defines a tool; serveStdio serves it over stdio.
• Four starting points: build a server, build a client, upgrade from v1, or drop into Express, Hono, Fastify, or Workers.

Source: docs/index.md