Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, and non-destructive behavior. The description adds meaningful behavioral context beyond annotations: the tool reports direct compatibility only on a verified interface match, and it operates on canonical ProductTwins, not arbitrary products. 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.