Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are present, so the description carries the full burden. It clearly indicates a read-only operation and a list result, but does not disclose potential authentication requirements, ordering, or the exact composition of the month list. For a zero-parameter read tool, this is minimally adequate but not rich.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.