Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly/idempotent/non-destructive, but the description adds what they cannot: it is advisory only, never modifies the draft, never blocks scheduling, and it instructs the agent how to handle output (offer topFixes, evaluate needsJudgment itself, never invent facts). That output-handling guidance is genuinely beyond the structured metadata.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.