Building an AI Agent from Scratch, Part 4: Remote Tools, or Trusting a Knife You Didn't Forge
In Part 2 we forged our own knives: a calculator that parses an AST instead of calling eval, file tools locked in a sandbox, every input frisked by code we wrote and could actually read. We trusted those tools because we built them. This post is about handing the model a knife from a stranger’s kitchen, sight unseen, and saying “go nuts.” That’s the Model Context Protocol, or MCP. It lets a tool live on someone else’s server, behind a login, and still show up on the model’s menu like it grew there. And here’s the part that should make the back of your neck prickle: ...