Ideally documentation should have a few key elements
- Grouping of articles with common themes
- Clear and meaningful titles. Rather than using the function names as a title, use the intended use instead.
- A brief description of what should happen, and what it is used for
- A short code sample, of how to implement it
- In UI affecting functions, a demonstration of how it should look and work
- In the case of style guidelines a do/don't example
- Any caveats that may be encountered
Always bear in mind that the documentation may be read by an intern when they start working with the project, so get into their mindset whilst developing it. Ask whether it would be simple to find what you're looking for, is it easily understandable, and does it show how to use it?