Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, and non-destructive. The description adds that data is estimated from published sources, not measurements, alerting the agent to potential inaccuracy. This context is valuable beyond annotations, though no further behavioral details are needed.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.