Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare destructiveHint=true and readOnlyHint=false, and the description goes further by specifying exactly what is destroyed (series + upcoming scheduled post, past posts retained), that the action is irreversible, and that out-of-workspace ids return "Recurring post not found". It also reports the return shape ({ deleted: true }). Rates just under 5 only because it omits permission/auth requirements and any cascade effects on analytics or linked drafts.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.