Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Beyond annotations, the description discloses important behavior: strict validation, structural errors not entering the run or consuming a step, valid-but-poor choices consuming a step, and return contents including events and completion rating. This gives rich operational context without contradicting the annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.