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 values and specifies the input format with an example. However, it does not mention potential errors, data source, or any edge cases. For a read-only lookup, this is fairly transparent but not exhaustive.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.