Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare this a read-only, non-destructive, closed-world operation, so the bar is lower. The description still adds real value by defining the output semantics precisely (INDEL frequency in percent) and pinning the model to wild-type SpCas9, which tells the agent the score is not transferable to other Cas variants. It does not discuss scoring scale interpretation or limits, which the output schema partly covers.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.