Tools and Function Calling

A tool is a named capability with a contract: a name, inputs, and a result the model can read. Function calling is how the model asks to use that capability instead of pretending it already knows the answer.

In this lesson you build a tiny inspector: a page that shows one real tool call (name, input, result) so you can see the glass window, not just the chat.

Learning outcomes

• Describe a tool as name + input schema + result
• Show a failed call vs a successful call
• Refuse to invent a result you did not run