This is really neat!
My current workflow uses phoenix_swagger to generate a swagger spec, then bureaucrat to generate markdown documentation.
With good tools available, there’s no excuse to not have a well documented REST API 
One idea I haven’t tied out yet is to replace custom mix tasks that generate json/markdown/html files with a more integrated mix compiler, this post makes it look pretty strait forward.
For prex, you might be able to use macros to generate the module body from the api blueprint, using @external_resource to cause a recompile when the blueprint changes.
