OK, as a starting point for that
We're in a holding pattern right now, but if you'd like to experiment with proposed markup for method signatures or hooking into an editor's auto-completion system or something like that, please do.  I'd love to see lots of experiments so that we have experience with all the great things that extracting this data might do for us
and WRT the "editor and auto-completion" part, I collected some bits from my init.el plus some links related to Emacs and Scheme plus some context and put that into that Org-mode file. Maybe we can use that as a starting point for the Emacs side. I'm fine with changing every single line of that, as I know that it's all quite hacky - but still helps for the few things I wanted to have, without having to configure all that many different Scheme modes. I'm also interested in finding what other more or less quick hacks built in the same vein we can collect.

If you think that it wouldn't complicate life even more to now also already start from that angle, I could either move the whole file to the schemedoc repo, or if Org-mode is not preferred, I could split the content into a markdown document and an .el file.