Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It discloses the return fields (name, description, downloads, rating, trust level) and the popularity-based sorting behavior for agent-optimized search. It doesn't cover potential errors or pagination, but it's still substantive.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.