Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare read-only, idempotent, and non-destructive behavior. The description adds that data comes from Wikipedia's On This Day feed, providing source transparency. No behavioral contradictions or additional traits like rate limits are disclosed, but for a read-only tool, this is sufficient.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.