Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations cover the safety profile (not read-only, not destructive, not idempotent), and the description adds genuinely new context: it consumes 'one generation from the monthly quota,' which explains the cost of repeat calls. No auth or failure behavior is described, but the quota disclosure is meaningful added value.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.