Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations only provide readOnlyHint=false, so the description carries the burden of behavioral disclosure. It adds valuable details: the automatic earning split (82%), the length constraints (min 8, max 8000), and the return shape. These go beyond what annotations reveal and help the agent understand side effects and expectations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.