headers.rb

module Acme
  class Headers < Grape::API
    format :json

    namespace :headers do
      desc 'Returns a header value.'
      params do
        requires :key, type: String
      end
      get ':key' do
        key = params[:key]
        { key => headers[key] }
      end

      desc 'Returns all headers.'
      get do
        headers
      end
    end
  end
end