How do AI agents use tool calling and function calling?
Tool calling enables AI agents to interact with external systems by invoking predefined functions. The LLM receives a description of available tools including their names, parameters, and purposes. When the agent determines that a tool is needed to fulfill a request, it generates a structured function call with the appropriate parameters. The system executes the function and returns the result to the agent, which then incorporates the result into its response or uses it for further reasoning. Examples include querying a database to look up customer information, calling a weather API for forecast data, sending an email through an email service, creating a calendar event, and performing calculations. Modern LLMs like GPT-4, Claude, and Llama 3.1 have native function calling capabilities. Tool definitions serve as the agent interface to the external world, and careful tool design is critical for agent effectiveness.