08-05
What Are Tools? A Precise Walkthrough of LLM Tool Calling
This article walks through LLM tool calling using a simple write-file example. Tools are not magic: each tool is defined by a name, a description, and JSON Schema parameters, then injected into the system prompt. When the model decides to act, it returns only a tool-call message with an id and parameters; nothing actually happens until the developer intercepts that message, executes a matching function, and sends the result back under the same id. Errors are sent back too, so the LLM can adapt its next step. The post is aimed at engineers starting to build agents who want a precise mental model of the loop.