How to use Claude tool-use in 5 steps

Wire up your first tool-using agent in under an hour. No prior agent experience needed.

Tools are how Claude reaches outside its own knowledge. A tool is just a structured description of something the model can call — give it a name, a docstring, and a JSON schema, and Claude figures out when to invoke it.

Try it yourself

Below is a runnable cell. Pick a model, edit the prompt if you like, and hit Run.

Why three fields, not one big string?

The schema is what makes the call type-safe. Without it, the model would emit free-form JSON your code couldn't validate. With it, every tool call either matches the schema or fails closed.

Continue with the next chapter to see how tool_result messages feed Claude's reasoning on the next turn.