Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, so the safe read nature is known. The description adds behavioral context by specifying the exact metrics (attention share %, rank, velocity) and the categorical outcome (rising/falling/stable/emerging), which is useful for setting expectations. 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.