Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already mark readOnlyHint=true and destructiveHint=false. The description adds behavioral details: rules are in evaluation order, triggers are ANDed, actions fire on match. This goes beyond annotations, though no rate limits or auth details are mentioned.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.