Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, closed-world, so the safety profile is covered. The description adds real value beyond that: it discloses per-call billing cost ('每次调用计费 1 次') and the aggregation window, both of which affect invocation decisions. It could go further on default lookback semantics, but the billing disclosure is a genuinely useful addition.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.