Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already mark the tool read-only, idempotent, open-world, and non-destructive; the description adds useful non-obvious details: no API key needed, case-insensitive capability matching, and a matched-subset return. No contradiction with annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.