Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations indicate readOnlyHint, openWorldHint, and idempotentHint. The description adds value by noting the async requirement and describing outputs (structured playbook steps, notification drafts, compliance checklists), which supplements the annotations without contradiction.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.