Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly/idempotent/non-destructive, so the safety bar is covered elsewhere. The description adds real behavioral context beyond that: published_version_id is null while a publication is still being prepared, and content is only present for markdown documents. That prevents wrong assumptions about nulls and missing fields.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.