Definition
Tool Calling
Tool calling, also called function calling, is how an agent acts on the world. The model reads the descriptions of available tools, decides one is needed, and emits structured parameters; your code executes the actual call and feeds the result back. The LLM decides, your code executes. That separation lets you add approval gates, rate limits, and audit logs between a decision and its execution.
Explained in
Chapter 9: What Is an Agent?
The moment you give an LLM access to knowledge or tools, it becomes an agent. And that makes all the difference.
Related terms