> If we're going to use it, we should allow readers of the API to expect it to be used thoroughly

I don't ascribe to the idea that unless something can be done right everywhere there is no point in doing the right thing in this case. But I agree it would be good to document the public API for writing Sass functions with release information.

> Also, can't we just put this on the module itself rather than each of the functions?

Maybe? I don't think that's as useful when reading the actual code instead of the generated docs.