Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Although annotations cover 'readOnlyHint: true,' the description adds crucial behavioral context by detailing the lack of financial friction ('no money moves,' 'free, keyless'), and the contents of the listing (deliverable, price, judge, deadline). This greatly enhances the agent's understanding of the operation's safety and function beyond metadata.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.