# Tool Search

> A search layer over available tool definitions that loads only the few relevant ones on demand instead of front-loading every definition into the prompt.

- Category: Tools & Protocols
- Stage: Rising
- Also called: Tool Search Tool, Dynamic tool discovery, Deferred tool loading
- Canonical: https://www.joelcsaji.com/ai-dictionary/tool-search

## Plain English

The agent looks up the right tools when it needs them instead of carrying a thousand-tool menu everywhere.

## Example

An agent with 1,000+ enterprise tools answers a tool-search query for 'refund', pulls in just the three Stripe tools it needs, and proceeds.

## Why it matters

Anthropic reports an 85% token reduction and higher tool-calling accuracy (49% to 74% on Opus 4) when discovery replaces a bloated catalog.

## Related

- [Tool Filtering](https://www.joelcsaji.com/ai-dictionary/tool-filtering)
- [Tool Use](https://www.joelcsaji.com/ai-dictionary/tool-use)
- [Progressive Disclosure](https://www.joelcsaji.com/ai-dictionary/progressive-disclosure)

## Sources

- [Anthropic: Advanced Tool Use](https://www.anthropic.com/engineering/advanced-tool-use)