This kinda just sounds like the Advance section.

Free is meant for one liners and such.

Casual one or two paragraphs

Advanced a minimum of two (but usually way more. They can write like eight each post I swear xD)

And Advanced is supposed to be for in depth world building, character building, and etc. 

So what you want kinda sounds like Advanced in my opinion.

Though each GM makes their own tweaks in standards.