Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Without annotations, the description carries the full burden. It fails to disclose whether this is a read operation (implied but not stated), what happens if no open orders exist, potential rate limits, or any side effects. The note about API key is minimal.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.