Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations (readOnlyHint, idempotentHint, destructiveHint) already cover safety profile, so the description adds value by describing the conditional behavior: returns authenticated:true and empty pending[] when connected, else returns connect_url. This provides concrete behavioral detail beyond annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.