For an AI system to take actions, it must be able to interact with external tools such as APIs, databases, or internal services. But a language model cannot call these tools directly. It needs a clear description of what tools exist, what they do, and how they should be used. This is where tool schemas come in.

A tool schema defines the name, purpose, and input parameters of a tool in a structured format that the model can understand. Well-designed schemas help the model choose the right tool, pass the correct arguments, and avoid mistakes during execution.

Poorly designed schemas, on the other hand, often lead to incorrect tool calls, missing parameters, or unpredictable behavior.

In this chapter, we will learn how to design clear, structured, and model-friendly tool schemas so that language models can reliably interact with external systems and perform tasks effectively.