AI & models
Tool use
function calling
Tool use is when an AI doesn't just talk but reaches for a tool to get something done — reading a file, running a command, searching the web. The model decides which tool fits, uses it, and reads the result back. It's what turns a chatbot into an
agent. Why it matters
Part of What an AI agent is → Tool use is why Claude Code can actually change your files instead of only telling you how. Each tool is also a spot where it pauses to ask permission.
see also