Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds a genuinely useful nuance beyond them: polling this tool has no side effect on the action's execution (it never runs, retries, or changes it), which is exactly what an agent needs to know before repeated calls. It does not cover error behavior for unknown or foreign action IDs.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.