Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full behavioral burden, and it does disclose the single most important trait: the secret is returned only once and must be stored immediately. However, it says nothing about authentication/permission requirements, whether key creation can be undone, or rate limits on key issuance.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.