Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint false. The description adds context by explaining the result is 'upcoming departures' and specifying the stop_id format. No contradictions, and it supplements annotations with concrete formatting details.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.