Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare read-only, idempotent, and non-destructive behavior. The description adds that execution is synchronous, task support is forbidden, and the returned JSON is internal application state for orchestration. This supplements the annotations, but it doesn't cover pagination, filtering behavior, or response structure beyond what the schema indicates.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.