MCP TypeScript SDK

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.