Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations declare readOnlyHint, idempotentHint, and destructiveHint false, so the safety profile is known. The description adds valuable behavioral context beyond annotations by specifying the exact response shapes in different states (authenticated:true with empty pending[] vs. connect_url), which is not covered by annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.