# Tool Use

> Letting a model request external functions, APIs, databases, browsers, or code execution.

- Category: Tools & Protocols
- Stage: Established
- Also called: Tool calling, Tool invocation
- Canonical: https://www.joelcsaji.com/ai-dictionary/tool-use

## Plain English

The model asks your software to do something it cannot do by itself.

## Example

The model calls `getInvoiceStatus` and then uses the returned status in its answer.

## Why it matters

Tools are what turn language models from answer engines into action-capable systems.

## Related

- [Function Calling](https://www.joelcsaji.com/ai-dictionary/function-calling)
- [Tool Result](https://www.joelcsaji.com/ai-dictionary/tool-result)
- [Action-Time Authorization](https://www.joelcsaji.com/ai-dictionary/action-time-authorization)

## Sources

- [OpenAI: Function Calling](https://developers.openai.com/api/docs/guides/function-calling)
- [Anthropic: Building Effective Agents](https://www.anthropic.com/engineering/building-effective-agents)