Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations mark readOnlyHint=false (a write) and destructiveHint=false, but the description adds substantial context beyond that: the key is 'one-time', 'returned once — store it securely', and the naming behavior ('an agent registered without one is stored named after its own id...'). This reveals side effects and security implications not captured in annotations, so it earns 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.