The only public documentation available currently is in the API guide.
The uri_filter is a way to filter the notifications based on its policy path (uri = policy path). Depending on your notification ID, will depend on whether you would need to supply a uri_filter. What do you mean by you want to customize the URI filter?
According to the API guide, this field is optional.
The is no more documentation publicly available than what is currently listed in the NSX-T API guide.