Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the behavioral burden. It discloses that results are capped, that topics carry full paths to disambiguate names, and that 'detail' adds biography/picture for authors. This is solid read-only behavioral context, though it does not discuss pagination or return shape, which the output schema may cover.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.