Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly=true, idempotent=true, and destructive=false. The description adds that it returns all four results at once, which is not captured in annotations, providing useful behavioral context. The schema separately documents the non-negative constraint for square root, so the description adds value 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.