Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false. The description adds behavioral context by specifying support for standard 5-field cron (minute hour day month weekday), which is useful beyond the annotations. It does not cover error behavior, but the output schema likely covers that.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.