Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds a genuine behavioral fact not in any structured field: gated items return metadata only, which materially shapes how an agent should interpret results. It stops short of disclosing pagination/cursor behavior or relevance ordering.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.