At least for PowerShell such a thing should be trivial as the shell knows about its commands and parameter parsing is consistent for every command.

I'll probably try hacking something together on the weekend for PS.

Awesome, thank you! :D

Not progressing as fast as I'd like. Stumbled over a few roadblocks regarding parameter binding. The rules are complex (and underdocumented, I might add. E.g. why man gci displays three parameter sets, or why -fi always binds to -filter and not to -file is unknown to me. CmdletInfo.ResolveParameter sounds like being great in theory but is unusable in practice. At least when I'm done I might be able to revisit parameter binding in Pash. Preliminary repo is at https://github.com/ygra/ExplainPS – once parameter binding is done the rest is just fetching information from Get-Help which is the actual trivial part.