Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations cover the safety profile (readOnlyHint=false, idempotentHint=false, openWorldHint=true), and the description adds substantial context beyond them: it queues paid runs that consume credits, operates asynchronously with a batch ID, supports an optional webhook that returns an HMAC webhookSecret for verification, and collapses duplicate URLs so totalUrls may be smaller than the input array. This is exactly the extra behavioral detail the annotations cannot convey.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.