If you are writing an API sandbox with a local development tool, you will no doubt need fixtures for your API’s modeling.
It turns out those fixtures are a great example of how your API is modeled. If you comment on those fixtures, they can be great documentation for the perusing developer.
I spent some time trying to automatically generate HTML documentation from YAML with inline comments. I got as far as generating a nice set of nested tables.
Feel free to use it :)