Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare read-only, idempotent, and non-destructive behavior. The description adds valuable behavioral context: the formula, the sign interpretation, and the tier requirement (HOBBY+) for history. It also clarifies that the default returns a single number, aligning with the histogram parameter.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.