API / new .command development?

Hi, new here so sorry if this is out of line - I'm interested in writing some new . commands - particularly ways to allow Spectrum BASIC programs to get directory listings into a string array, things that would help navigating a drive, enumerating files etc. With the imminent Next I think there might be a nice flux of new basic programmers and with esxDOS being bundled in with the Next, I think it would be cool if there were a few tools to help people use the disk filing system with their own programs.

How would I go about grabbing some documentation for the project? I'm not a timewaster, I am a developer :-) - initially, I am particularly interested in writing something to allow a BASIC program to dump a directory listing into a basic string array, etc - a kind of '.lsarray' if you like.