Agents & tools
Tool Use
The ability of an AI model to call external tools — like a calculator, search engine, or API — to help answer a question.
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In plain English
Tool use (also called function calling) is when an AI model doesn't just generate text — it also invokes external tools to get real information or take real actions.
Common tools an AI might use:
- Web search to find current information
- A calculator for precise maths
- A code interpreter to run Python
- A calendar API to check availability
- A database to look up a customer record
Why it matters: LLMs have a knowledge cutoff and can't do exact arithmetic reliably. By giving them tools, you get accurate, up-to-date, actionable AI rather than an AI that guesses.
Tool use is the foundation of most useful AI agents and assistants.
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Related terms
Function Calling
A feature that lets an AI model trigger specific functions or APIs in your app instead of just returning text.
Agent
An AI system that can take actions, use tools, and make decisions autonomously to complete a goal.
MCP
Model Context Protocol — an open standard that lets AI models connect to external tools and data sources in a consistent way.
API
An interface that lets developers send requests to an AI model and get responses programmatically — the way most AI tools talk to LLMs.
Back to glossaryLast reviewed May 2026