Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnly, non-destructive, closed-world), yet the description adds real behavioral context beyond them: that results are private to this agent identity, that preview_truncated marks clipped previews, and that ranking, review_due, and previews are not truth judgments. Those are semantic caveats an agent could not derive from the annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.