Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden and does so: read-only, no quota deduction on invalid codes, 422 on multi-code, historical-snapshot edge cases (future date → latest trading day, pre-listing → all zeros with ok:false), and return-shape differences when `date` is passed. This is behavior an agent cannot infer from any structured field.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.