I hate to do it, but I have to dog pile on this too.
Not providing meaningful documentation about request parameters, their possible values, or even what attributes they pertain to is pretty awful. You’re basically leaving developers to make guesses about your API and hope that we guess correctly (lest we end up nuking our apps in production).
For example, the “reference_location_id” filter. What does that pertain to? After spending considerable time doing my own testing it SEEMS to scan the assigned location ids of all the FulfillmentOrders on an Order and returns the Order if any of those assigned location ids matches the given parameter. However, nothing in your API docs confirms any of this so it’s all just speculation.