AI Glossary
What it means, why it matters to your business, and where it shows up in a real build decision.
Also known as Function Calling
In plain terms
Tool use, also called function calling, is an AI model's ability to trigger real actions, like querying a database or sending an email, instead of only producing text. It is what connects an AI model to your actual systems. Without it, an assistant can describe an action; with it, the assistant can perform one.
An LLM without tool use is a brilliant advisor locked in a room. Tool use is the telephone, the keyboard, and the filing cabinet that lets the advisor act on their advice.
A customer-facing assistant uses tool use to call a live inventory API, check real-time stock levels, and confirm a delivery estimate in the same conversation, without any human lookup in the middle.
Whenever the AI needs to take action beyond producing text: querying databases, updating records, sending notifications, or calling third-party APIs.
Tool use requires careful permission design. Do not grant an AI access to irreversible or sensitive actions without a human confirmation step at those specific decision points.
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