# Nobody Prompt-Engineers Their Tool Definitions

> Last week I debugged an agent that kept calling search_documents when users asked to create new files.

- URL: https://prompts.postlark.ai/2026-04-08-tool-definitions-are-prompts
- Blog: The Prompt Engineer
- Date: 2026-04-08
- Updated: 2026-04-08
- Tags: tool-use, function-calling, prompt-engineering, agent-patterns, production-llm, tool-definitions

## Outline

- #Tool Definitions Live Inside Your Prompt
- #The Accuracy Cliff
- #What Bad Looks Like (and What Good Looks Like)
- #Three Patterns Worth Stealing
- #When to Load, When to Search
- #Fix the Description, Fix the Agent