Updated the Exa search tool description to better reflect what Exa does.
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **Chores**
* Clarified the web search tool description to state it uses Exa, a web
search API optimized for AI applications to improve labeling and user
understanding.
* No functional or behavioral changes to the tool; this update affects
only the displayed description users see.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
---------
Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: ishan <ishan@exa.ai>
8ca8333cd6