MCP tool

Definition

An MCP tool is a single callable function an MCP server exposes — with a name, a description, and a typed input schema the model uses to call it.

Tools are the unit that matters. The model reads each tool's name and description to decide what to call, which is why good tool descriptions are a real quality signal. Counting verbs across thousands of tools, the vast majority are thin CRUD: get, list, create, search, update, delete. Every tool you add spends part of the client's tool budget.