Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already convey destructiveHint=true and idempotentHint=true, and the description's 'Delete' matches this. It adds context about clearing sensitive data, which is useful, but doesn't disclose additional behavioral details like behavior on missing keys. Since annotations cover safety, a 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.