Model Context Protocol (MCP) is the open standard Anthropic introduced in late 2024 for giving language models access to tools, data sources, and prompts in a vendor-neutral way. Before MCP, every chat application built its own bespoke integration layer; MCP defines a small JSON-RPC protocol that any client (Claude Desktop, Cursor, Zed, custom apps) can use to talk to any server (databases, file systems, third-party APIs) without re-implementing the integration each time.
The protocol has three primitives — tools (functions the model can call), resources (data the model can read), and prompts (templated workflows). The ecosystem grew quickly: official servers exist for Postgres, GitHub, GitLab, Slack, Google Drive, and dozens of niche tools, plus a long tail of community-built ones.