Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Without annotations, the description must carry the behavioral burden. It implies a read-only computation, which is likely correct, but does not specify behaviors such as handling of empty arrays, NaN values, or return type. The presence of an output schema mitigates some concern about return format, but the description adds no behavioral detail beyond the basic operation.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.