RailsApi - include helpers
#include ActionController::Helpers and
#provide your own Helper modules to the view using the 'helper' method
#In my API application I created a RenderingController which acts as a superclass for all controllers that do render:
class RenderingController < ApplicationController
include AbstractController::Layouts
include AbstractController::Translation
include ActionController::ImplicitRender
include ActionController::Helpers
helper ApplicationHelper, OtherHelper
end