Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations provide readOnlyHint=false, but the description adds substantial behavioral detail beyond that: the request drops off the public board, can no longer be upvoted, is NOT hard-deleted, is idempotent (withdrawing an already-withdrawn request succeeds), and is free. This gives the agent a clear mental model of side effects, which is especially valuable for a mutation.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.