I actually have an approach here: ASCII diagrams, so i can embed them in code or a README. It keeps things simple - you can't have a super complex ASCII diagra

I actually have an approach here: ASCII diagrams, so i can embed them in code or a README. It keeps things simple - you can't have a super complex ASCII diagram; even crossing lines look terrible - and there's at least a fighting chance that when someone changes the code they will at least notice the diagram is out of date. To prevent insanity, I use a tool to help draw them: Monodraw in my case.