Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full behavioral burden. The word 'Get' and the qualifier 'open' convey a read-only operation returning only open order-book entries, which is useful. However, it does not describe anything about the response format, ordering, pagination, or error behavior.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.