Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, open-world, non-destructive, so the safety profile is covered. The description still adds real behavioral context the annotations cannot: pricing ($0.025/call, 10 free/day, x402 options surfaced on payment-required results) and failure semantics (isError with message, not charged). What it does not add is any note on output size or latency for a multi-source bundle.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.