Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already indicate destructive and idempotent behavior, so the bar is lower. The description adds minimal extra behavioral context beyond the core delete action. It mentions 'previously stored' which implies the key must exist, but does not disclose error handling, return values, or what happens if the key is missing. Since annotations cover the main safety profile, a score of 3 is appropriate.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.