In practice
It defines how a client and server describe available tools, make calls and return results. A common comparison is a port standard: build to the shared connection once instead of creating a different integration for every pairing.
MCP isn't a model, agent or product. It is a specification. The useful parts are the clients and servers built on it.
Why it matters for product builders
The integration problem changed from every app connecting separately to every source, to clients and servers each supporting 1 shared protocol. That is a major reason agent tooling expanded so quickly through 2025.
**Source note**
Anthropic published the [Model Context Protocol](https://modelcontextprotocol.io) as an open standard in November 2024.