Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations only cover the generic flags (readOnlyHint=false, idempotentHint=false). The description adds genuinely useful behavior beyond them: the key is returned only once, it is a secret credential, and there is a per-network monthly issuance limit. It does not say what the response payload looks like or how to use the key afterward, keeping it short of a 5.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.