Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations (destructiveHint=true, openWorldHint=true, readOnlyHint=false) mark this as a state-changing, outward-facing call, and the description adds substantial extra context: missed slots are not published, the next occurrence becomes a SCHEDULED post ~24h ahead, ENDED is returned when the series is exhausted, and workspace-scoped ids yield 'Recurring post not found'. This is exactly the behavioral disclosure the annotations cannot carry.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.