Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden and does reasonably well: it enumerates the returned fields (source, date, licence, citation), which is the key behavioral fact for a zero-parameter getter. It omits auth/rate-limit considerations, but for a static read-only metadata call the gap is minor.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.