Content
# MCP TypeScript SDK
> [!IMPORTANT] **This is the `main` branch which contains v2 of the SDK (currently in development, pre-alpha).**
>
> We anticipate a stable v2 release in Q1 2026. Until then, **v1.x remains the recommended version** for production use. v1.x will continue to receive bug fixes and security updates for at least 6 months after v2 ships to give people time to upgrade.
>
> For v1 documentation, see the [V1 API docs](https://ts.sdk.modelcontextprotocol.io/). For v2 API docs, see [`/v2/`](https://ts.sdk.modelcontextprotocol.io/v2/).
  
<details>
<summary>Table of Contents</summary>
- [Overview](#overview)
- [Packages](#packages)
- [Installation](#installation)
- [Quick Start (runnable examples)](#quick-start-runnable-examples)
- [Documentation](#documentation)
- [Contributing](#contributing)
- [License](#license)
</details>
## 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:
- MCP **server** libraries (tools/resources/prompts, Streamable HTTP, stdio, auth helpers)
- MCP **client** libraries (transports, high-level helpers, OAuth helpers)
- Optional **middleware packages** for specific runtimes/frameworks (Express, Hono, Node.js HTTP)
- Runnable **examples** (under [`examples/`](https://github.com/modelcontextprotocol/typescript-sdk/tree/main/examples))
## Packages
This monorepo publishes split packages:
- **`@modelcontextprotocol/server`**: build MCP servers
- **`@modelcontextprotocol/client`**: build MCP clients
Tool and prompt schemas use [Standard Schema](https://standardschema.dev/) — bring Zod v4, Valibot, ArkType, or any compatible library.
### Middleware packages (optional)
The SDK also publishes small "middleware" packages under [`packages/middleware/`](https://github.com/modelcontextprotocol/typescript-sdk/tree/main/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`](packages/middleware/README.md) for details.
- **`@modelcontextprotocol/node`**: Node.js Streamable HTTP transport wrapper for `IncomingMessage` / `ServerResponse`
- **`@modelcontextprotocol/express`**: Express helpers (app defaults + Host header validation)
- **`@modelcontextprotocol/hono`**: Hono helpers (app defaults + JSON body parsing hook + Host header validation)
## Installation
### Server
```bash
npm install @modelcontextprotocol/server
# or
bun add @modelcontextprotocol/server
# or
deno add npm:@modelcontextprotocol/server
```
### Client
```bash
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, 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`](packages/middleware/README.md) for details.
```bash
# Node.js HTTP (IncomingMessage/ServerResponse) Streamable HTTP transport:
npm install @modelcontextprotocol/node
# Express integration:
npm install @modelcontextprotocol/express express
# Hono integration:
npm install @modelcontextprotocol/hono hono
```
## Quick Start (runnable examples)
The runnable examples live under `examples/` and are kept in sync with the docs.
1. **Install dependencies** (from repo root):
```bash
pnpm install
```
2. **Run a Streamable HTTP example server**:
```bash
pnpm --filter @modelcontextprotocol/examples-server exec tsx src/simpleStreamableHttp.ts
```
Alternatively, from within the example package:
```bash
cd examples/server
pnpm tsx src/simpleStreamableHttp.ts
```
3. **Run the interactive client in another terminal**:
```bash
pnpm --filter @modelcontextprotocol/examples-client exec tsx src/simpleStreamableHttp.ts
```
Alternatively, from within the example package:
```bash
cd examples/client
pnpm tsx src/simpleStreamableHttp.ts
```
Next steps:
- Server examples index: [`examples/server/README.md`](examples/server/README.md)
- Client examples index: [`examples/client/README.md`](examples/client/README.md)
- Guided walkthroughs: [`docs/server.md`](docs/server.md) and [`docs/client.md`](docs/client.md)
## Documentation
- Local SDK docs:
- [docs/server.md](docs/server.md) – building MCP servers: transports, tools, resources, prompts, server-initiated requests, and deployment
- [docs/client.md](docs/client.md) – building MCP clients: connecting, tools, resources, prompts, server-initiated requests, and error handling
- [docs/faq.md](docs/faq.md) – frequently asked questions and troubleshooting
- External references:
- [SDK API documentation](https://ts.sdk.modelcontextprotocol.io/)
- [Model Context Protocol documentation](https://modelcontextprotocol.io)
- [MCP Specification](https://spec.modelcontextprotocol.io)
- [Example Servers](https://github.com/modelcontextprotocol/servers)
### Building docs locally
To generate the API reference documentation locally:
```bash
pnpm docs # Generate V2 docs only (output: tmp/docs/)
pnpm docs:multi # Generate combined V1 + V2 docs (output: tmp/docs-combined/)
```
The `docs:multi` script checks out both the `v1.x` and `main` branches via git worktrees, builds each, 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/`](https://ts.sdk.modelcontextprotocol.io/). The v1 source code and any v1-specific fixes live on the long-lived
[`v1.x` branch](https://github.com/modelcontextprotocol/typescript-sdk/tree/v1.x). V2 API docs are at [`/v2/`](https://ts.sdk.modelcontextprotocol.io/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](LICENSE) file for details.
