Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already establish readOnlyHint=true, and the description adds genuinely new behavioral context: a per-call cost of 1 cent, which matters for an agent deciding how often to call. The default fan-out behavior when chain is omitted is also disclosed. It stops short of describing rate limits or billing mechanics, but the cost disclosure is the important one.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.