Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden of disclosing behavioral traits. It doesn't indicate whether the update is partial or full, what happens to omitted fields, authorization requirements, or any side effects. The nested schema implies a full replacement (title and exercises required), but that is not disclosed in the description.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.