The Model Context Protocol TypeScript SDK is the official implementation of the MCP specification, enabling applications to provide standardized context to language models. The repository is currently in a significant transition phase, with the main branch hosting v2 of the SDK, which implements the 2026-07-28 MCP specification and remains in beta. The v2 packages, published as @modelcontextprotocol/server and @modelcontextprotocol/client, are expected to reach stable release on July 28, 2026, while v1.x continues to receive bug fixes and security updates for at least six months after v2 ships. This dual-version approach reflects the project's commitment to stability during a major specification update.
The SDK is structured as a monorepo that publishes split packages for building both MCP servers and clients. The server package provides libraries for implementing tools, resources, and prompts, along with support for multiple transport mechanisms including Streamable HTTP, stdio, and authentication helpers. The client package supplies transports, high-level helpers, and OAuth utilities for connecting to MCP servers. Both packages support flexible schema validation through Standard Schema, allowing developers to bring their own validation library such as Zod v4, Valibot, or ArkType.
Beyond the core packages, the SDK includes optional middleware packages designed as thin adapters for specific runtimes and frameworks. These middleware packages—@modelcontextprotocol/node for Node.js HTTP, @modelcontextprotocol/express for Express integration, and @modelcontextprotocol/hono for Hono support—are intentionally minimal and avoid introducing new MCP functionality or business logic. This design philosophy keeps the middleware focused on wiring MCP into existing frameworks rather than extending the protocol itself.
The repository runs on Node.js, Bun, and Deno, providing broad runtime compatibility for developers building MCP applications. The project includes comprehensive documentation with step-by-step tutorials for building both servers and clients, along with runnable end-to-end examples demonstrating real-world usage patterns. The documentation site at ts.sdk.modelcontextprotocol.io/v2/ covers tools, resources, prompts, HTTP and stdio serving, client implementation, OAuth integration, and migration guidance.
Currently, the project is managing pull requests conservatively during the v2 specification implementation phase, limiting new contributors to one pull request each while the team stabilizes the 2026-07-28 spec. The maintainers actively encourage feedback through GitHub issues, which they identify as the most useful form of contribution at this stage. The codebase is licensed under Apache License 2.0 for new contributions, with existing code remaining under MIT, providing clarity on licensing terms for both legacy and new code.
