Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, and non-destructive hints. The description adds meaningful context beyond annotations: no authentication needed, prices are display-only with the authoritative amount computed at purchase, and results are ordered cheapest first. No contradiction exists.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.