Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so the safety profile is covered. The description adds genuinely new behavioral context: that billing is usage-based with a default estimate of $0.04 and that final cost may vary. That cost disclosure is useful beyond the annotations, though return format, result caps and throttling are still unstated.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.