Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare destructiveHint=true and idempotentHint=false, but the description adds genuinely new operational context: each invocation spawns an additional run with real side effects, and user confirmation is expected first. That is the key non-obvious behavior for a repeat-callable mutation. It does not describe failure modes or what the returned run looks like, so not 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.