Last month I wired Claude up to my email infrastructure. Not "Claude writes an email draft and I paste it somewhere" but the agent checks my domain status, sends the email, and reads back the delivery events, all from the chat.
The glue that makes this possible is MCP (Model Context Protocol), and the whole setup takes about five minutes. Here is exactly how to do it, plus what surprised me once agents could actually touch production infrastructure.
What MCP actually is
MCP is a small JSON-RPC protocol that lets an AI client (Claude, Cursor, Windsurf, your own agent) call tools exposed by a server. The server describes its tools with JSON schemas, the model picks a tool and fills in the arguments, and the client executes the call.
The important design decision is where the server runs. A lot of MCP servers are local stdio processes you install per machine. For anything talking to a hosted API, a hosted MCP server is the better shape: nothing to install, your API key is the auth, and every client that speaks HTTP can use it.
