modelcontextprotocol.io

If modelcontextprotocol/servers is the example code, this is the specification. The site describes MCP as “an open-source standard for connecting AI applications to external systems”, and offers the analogy that has done more to explain it than any diagram:

Think of MCP like a USB-C port for AI applications.

Why this belongs in the directory separately from the Claude docs

Because MCP is not a Claude feature. The site documents clients well beyond Anthropic — ChatGPT, Visual Studio Code, Cursor and others — and the spec is versioned independently of any vendor’s release cycle. Documentation paths carry a dated spec version (2026-07-28 at the time of checking), so an MCP server you write targets a protocol version, not a product version.

For Claude Code users that distinction matters when something breaks: the question “is this a Claude Code bug or a protocol misunderstanding” is answered here, not in the Claude docs.

What it hosts

• The specification, versioned by date
• Guides for building servers and building clients
• MCP Apps — interactive apps that run inside an AI client, an extension beyond tools and resources
• Architecture and concept documentation

Where to start

If you are connecting Claude to something, start with Claude Code’s MCP quickstart. If you are writing a server that should work in more than one client, start here instead.