Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover read-only, idempotent, and non-destructive behavior, so the bar is lower. The description adds meaningful behavioral detail by specifying exactly what is returned: description, price, and each variant/option with price and stock status.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.