Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description adds value beyond annotations by specifying determinism ('the same product set, ordering, and filters a shopper sees'), pagination ('24 per page'), and the need for a permalink. Annotations already declare readOnly and idempotent hints, and the description complements these without contradiction.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.