Gather information relevant to the API
Custom output templates provide the flexibility to return whatever data you wish, so it is important to understand that it is possible to modify an output template in such a way that it returns information that is not quite relevant to the API.
For example, it is possible to modify the output template of the getOrderList() API in such a way that it returns detailed information about an order rather than just header-level information. You should modify an output template in such a way that it takes advantage of the unique aspects of its corresponding API. Keeping each template unique to its API prevents any ambiguity about which API to use in any specific situation.