How do you know when you've done enough to describe the subject matter in a painting? There always seems to be a little more that wants to be included. I think the key is to look inside rather than at the scene or the photo. You have to trust your gut feelings.
In the alleyway sketch, above, the most important aspect is the sunlight. That's the story I want to tell, so if the shapes appear to be lit by strong light, the essential information is there. I could stop even though there is plenty more optional information I can see. On the sunlit side of the garage the siding is described with a few swift strokes. I haven't made clear whether the siding has corner boards or mitered corners. Should I add more information to make sure the viewer can tell?
What about that brown shape in the lower right? I'm guessing no one but me knows what that is, but the sun is shining on it, and it contributes to the feeling of a cluttered alley. That's enough.
In this scene of headlands in fog Eliot O'Hara uses the foreground shape to tell us what the shapes in the background are. Only the closest form needs any detail for the viewer to know all they need to understand what the rest of the painting is about. Try closing one eye and covering the foreground. Without that information the background is insufficiently described, but when there is a clear context there is atmosphere and light and space. This is a painter who knows when to stop.
The following images present opportunities to tell a story that can be complete even though there is more that could be added. Decide for yourself what the most important thing is. Once that is present, that could be a good place to stop. Err on the side of too little information rather than too much.