Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false, and openWorldHint=false, so the safety profile is covered elsewhere. The description's only extra signal is 'immediate', and it says nothing about whether the call blocks or returns a job handle, how long a backup takes, or whether repeated calls queue duplicate backups (idempotentHint=false makes that a real question).
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.