Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden, and it does disclose the return contents, which is real behavioral information since there is no output schema. It does not state that this is a read-only, side-effect-free operation, nor anything about response size or latency, so it is not fully self-sufficient.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.