Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so the safety profile is covered. The description adds genuinely new behavioral context: the method (thousands of random paths), the ~10 trading day horizon, and the two outputs it estimates. It stops short of noting that results are stochastic or whether the simulation repeats identically across calls.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.