Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations only declare readOnlyHint=false, destructiveHint=false, openWorldHint=true; the description adds substantive context beyond that — it discloses the auth requirement, that the call never places a provider order or takes payment (bounding the side effect), and an availability precondition. It does not cover idempotency, whether the underlying quote is mutated, or what notification is emitted, so it stops short of 5.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.