Lesson 15: tool use — giving Claude tools
A model on its own only returns text — it doesn't know the weather right now, and can't send an email. tool use solves this: the model asks to run an external tool (a calculator, a search, a weather lookup), you run the tool and hand back the result, and it weaves that into its answer. In this lesso
Like asking a friend the current temperature: they don't know offhand, so they check their phone and then answer. The model does the same with a 'tool' — it asks, gets a result, and answers.
- tool use
- The model's ability to ask to run an external tool (search, calculator, an action), to reach information or do something plain text alone can't.
- the tool loop
- The model asks for a tool and inputs → you run it → you return the result → the model uses it in its answer.
- tool description
- What you tell the model about the tool in plain terms: its name, what it does, and what input it needs.
