des.rb

###############
##   WRONG   ##
###############
  
  class API::ArticlesController
    def create
      article = Article.new(article_params)
      
      if article.save
        render json: article
      else
        render json: { errors: article.errors.full_messages }
      end  
    end
  end

###############
##   RIGHT   ##
###############

  class API::ArticlesController
    def create
      article = Article.new(article_params)
      
      if article.save
        render json: article, status: 201
      else
        render json: { errors: article.errors.full_messages }, status: 422
      end  
    end
  end