Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false, openWorldHint=true), so the bar is lower. The description adds no additional behavioral context, such as whether cancellation is immediate, whether it requires the job to be active, or what happens on an already-cancelled job.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.