typescript-sdk README

The project's README from github.com/modelcontextprotocol/typescript-sdk. As one markdown file: README.md.

MCP TypeScript SDK

[!IMPORTANT] This is the main branch — v2 of the SDK (@modelcontextprotocol/server, @modelcontextprotocol/client), implementing the 2026-07-28 MCP spec.

Have feedback? Please open a v2 issue — it is the most useful thing you can do for the SDK right now. The v2 documentation starts with a ten-minute server tutorial.

v2 is the stable release line, released alongside the 2026-07-28 spec. v1.x continues to receive bug fixes and security updates for at least 6 months after v2's release. v1 documentation: ts.sdk.modelcontextprotocol.io · v2: /v2/.

[!WARNING] We're limiting pull requests to 1 per new contributor while v2 settles after the 2026-07-28 spec release.

Issues are the most useful feedback right now — we'll reopen PRs as v2 stabilizes.

NPM Version - Server NPM Version - Client MIT licensed

Table of Contents

Overview

The Model Context Protocol (MCP) allows applications to provide context for LLMs in a standardized way, separating the concerns of providing context from the actual LLM interaction.

This repository contains the TypeScript SDK implementation of the MCP specification. It runs on Node.js, Bun, and Deno, and ships:

Packages

This monorepo publishes split packages:

Tool and prompt schemas use Standard Schema — bring Zod v4, Valibot, ArkType, or any compatible library.

Middleware packages (optional)

The SDK also publishes small "middleware" packages under packages/middleware/ that help you wire MCP into a specific runtime or web framework.

They are intentionally thin adapters: they should not introduce new MCP functionality or business logic. See packages/middleware/README.md for details.

Installation

Server

npm install @modelcontextprotocol/server
# or
bun add @modelcontextprotocol/server
# or
deno add npm:@modelcontextprotocol/server

Client

npm install @modelcontextprotocol/client
# or
bun add @modelcontextprotocol/client
# or
deno add npm:@modelcontextprotocol/client

Optional middleware packages

The SDK also publishes optional “middleware” packages that help you wire MCP into a specific runtime or web framework (for example Express, Fastify, Hono, or Node.js http).

These packages are intentionally thin adapters and should not introduce additional MCP features or business logic. See packages/middleware/README.md for details.

# Node.js HTTP (IncomingMessage/ServerResponse) Streamable HTTP transport:
npm install @modelcontextprotocol/node

# Express integration:
npm install @modelcontextprotocol/express express

# Fastify integration:
npm install @modelcontextprotocol/fastify fastify

# Hono integration:
npm install @modelcontextprotocol/hono hono

Getting Started

Here is what an MCP server looks like. This minimal example exposes a single greet tool over stdio:

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

const server = new McpServer({ name: 'greeting-server', version: '1.0.0' });

server.registerTool(
    'greet',
    {
        description: 'Greet someone by name',
        inputSchema: z.object({ name: z.string() })
    },
    async ({ name }) => ({
        content: [{ type: 'text', text: `Hello, ${name}!` }]
    })
);

async function main() {
    const transport = new StdioServerTransport();
    await server.connect(transport);
}

main();

Ready to build something real? Follow the step-by-step tutorials:

For runnable, end-to-end examples beyond the tutorials, see:

Documentation

Building docs locally

To work on the documentation site locally:

pnpm docs:api      # Generate the API reference markdown (output: docs/api/)
pnpm docs:dev      # Start the VitePress dev server for the V2 site
pnpm docs:build    # Build the V2 site (output: docs/.vitepress/dist/)
pnpm docs:multi    # Build the combined V1 + V2 site (output: tmp/docs-combined/)

The docs:multi script builds the V2 site from the current checkout, checks out the v1.x branch via a git worktree to build the V1 site, and produces a combined site with V1 docs at the root and V2 docs under /v2/.

v1 (legacy) documentation and fixes

If you are using the v1 generation of the SDK, the v1 API documentation is available at https://ts.sdk.modelcontextprotocol.io/. The v1 source code and any v1-specific fixes live on the long-lived v1.x branch. V2 API docs are at /v2/.

Contributing

Issues and pull requests are welcome on GitHub at https://github.com/modelcontextprotocol/typescript-sdk.

License

This project is licensed under the Apache License 2.0 for new contributions, with existing code under MIT. See the LICENSE file for details.

typescript-sdk (modelcontextprotocol/typescript-sdk)

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13.6K ·GitHub
Typescript-sdk
What is this?This is the official TypeScript SDK for the Model Context Protocol (MCP), letting apps provide standardized context to LLMs by building MCP servers and clients.
Is this one SDK, or split into separate packages?It is a monorepo that publishes separate @modelcontextprotocol/server and @modelcontextprotocol/client packages, plus optional thin middleware adapters for Express, Fastify, Hono, and Node's http module.
How do I build my first MCP server with it?Follow the official step-by-step tutorial: install the server package and expose a minimal example, like a single greet tool served over stdio, in about ten minutes.
Which JavaScript runtimes does it support?It runs on Node.js, Bun, and Deno — package.json requires Node >=20 if you go that route, with no other runtime dependencies.
Is v2 ready to adopt right now?v2 is the new stable line matching the 2026-07-28 spec, but it's still settling: the maintainers are currently capping external pull requests at one per new contributor and prefer issue feedback. v1.x keeps getting bug/security fixes for at least 6 months after v2's release.
What transports does the SDK support for MCP communication?Both stdio and Streamable HTTP transports are built in, alongside OAuth helpers for securing client-server connections.
Do middleware packages like Express or Hono add extra MCP features?No — they're intentionally thin adapters handling things like Host header validation and body parsing, and shouldn't introduce new MCP functionality or business logic.
Can I use any schema library for tools and prompts?Yes, schemas use the Standard Schema interface, so Zod v4, Valibot, ArkType, or any compatible library works instead of being locked to one validator.
Where can I find runnable examples beyond the tutorials?The examples/ directory has self-verifying client/server example pairs, one story per directory, documented in examples/README.md.
What are similar projects?executor, http-proxy-middleware, mcp-use, mcporter, TetreesAgent_EX, trueforge, python-sdk, excalidraw-mcp
Which topics is it in?fastify, hono, mcp-client, express, oauth, monorepo, model-context-protocol, sdk, mcp-server, mcp, npm, apache-2.0
Creator
modelcontextprotocol
Size
19.8 MB
Stars
13.6K
Updated
CommitOct 13Releasev2.3.1Oct 05
Age
2y
Commits · 90 Days