This is what I learned to watch for with the end
- Confirm all questions are answered. Especially the main question that may not have been expressed. Don't leave the reader with unanswered concerns.
- Make sure the subplots are also closed or resolved.
- The end needs to be satisfying. Not that all endings have to end well, but it needs to follow the flow of the book. If you can, make the ending a surprise, even if you're giving the reading the ending they way.
In such a short story, I also need to remember to keep the dialogue tight.