I think the most important thing is:
- Explain what the file does. Most importantly, explain how it solves the problem stated in the question.
- Provide documentation of how to use it.
- Provide the source code, if possible. This enables peer review.
If none of these is the case, it's possible your answer is flagged for deletion. We generally review late answers or answers by new users, and anything suspicious gets removed quite efficiently.
If you're a regular user, your answer won't land in a review queue. Your duty should be to provide a good answer that doesn't only consist of "Here file, you download".