Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare read-only, open-world, and idempotent hints. The description adds meaningful behavioral context: all listings are free, and tier-gating restricts visibility. It also clarifies the default sort order and query semantics, going beyond annotations 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.