Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare read-only, idempotent, non-destructive behavior, and the description adds real context beyond them: synchronous execution, task support forbidden, and the output being internal application state that should not be surfaced as raw JSON. It still omits anything about pagination or result-set size relative to the 'limit' parameter.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.