Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden, but it only adds the operational detail that it makes one API call. It does not explain whether the operation is read-only, what exact statistics are returned, or any authentication/rate-limit implications, or missing for a fully transparent description.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.