Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already establish read-only, idempotent, non-destructive behavior; the description adds domain behavior by stating which forensic signals it computes and what question it answers. It does not discuss data freshness, sourcing, or limits, preventing a 5.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.