Definition
Tool use (also called tool calling) is the capability of an AI model to invoke external tools and APIs during a conversation. Instead of just generating text, the model can decide to search the web, read a database, send an email, create a spreadsheet entry, or interact with any connected service, then incorporate the results into its response.
Example
When you ask an AI agent "What's our revenue this quarter?", the agent calls your CRM API to pull sales data, queries your accounting system for invoiced amounts, and combines both into a summary answer.
Why it matters
Tool use is what separates a chatbot from an agent. Without tool use, AI is limited to its training data. With tool use, AI can access real-time information and take real-world actions.