Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The annotations already declare read-only and idempotent behavior, and the description adds clarity that both the standard week number and ISO week number are returned. No destructive side effects or auth requirements apply. The description doesn't discuss edge cases like invalid dates, but given the simplicity, this is acceptable.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.