Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld). The description adds genuinely useful behavior beyond them: the result is served from a cached saved list unless refresh is set, and canPublish=false means editorial review with content held unpublished until editor acceptance. That caching/staleness disclosure is the kind of trait annotations cannot express.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.