MCP host

Definition

The MCP host is the AI application (e.g. Claude Desktop or Cursor) that contains the model and the MCP client, and decides when to call tools.

Host vs client is a subtle distinction people mix up: the host is the whole app and the model; the client is the protocol-speaking part inside it. The host is what enforces things like the tool budget — which is why running too many servers degrades tool selection at the host level, not the server level.