The "show_definition" popup does know about the location of a symbol as displayed in the links, only. It has no idea about function arguments nor does/can it know about any documentation of it.
You can create plugins, providing popups with simple html content or use mdpopups plugin to use markdown to render some content. Those plugins could include a list of definitions as "show_definitions" popup.
But someone needs to provide the content to show. There are several approaches to provide those popups, but most of them target single languages only and use totally different backends.