This message was deleted.

the reason why I'm using a file is a very big size of json and actually I need to choose one of several files with different json content depended of request data

Unfortunately this isn’t supported in the webhook definition JSON at the moment. We’re planning to rework and expand the body model used in the response so that it can be used here and in a couple of other places, but that’s still TBD at the moment.

Thanks for your answer!