Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already disclose the mutation profile (readOnlyHint=false, idempotentHint=false, destructiveHint=false). The description adds useful context beyond them: it returns updated advice and must be called sequentially for every pick, implying stateful accumulation. It still doesn't describe what the 'advice' contains or failure behavior.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.