Grape root route

api.rb

#app/api/grape_test_api/api.rb

module GrapeTestAPI
  class API < Grape::API
    version 'v1', using: :header, vendor: 'twitter'
    format :json

    get 'hello' do
      "hello world"
    end

    get do
      "hello root"
    end
  end
end

application.rb

require File.expand_path('../boot', __FILE__)

require 'rails/all'

# Require the gems listed in Gemfile, including any gems
# you've limited to :test, :development, or :production.
Bundler.require(:default, Rails.env)

module GrapeTest
  class Application < Rails::Application
    # Settings in config/environments/* take precedence over those specified here.
    # Application configuration should go into files in config/initializers
    # -- all .rb files in that directory are automatically loaded.

    # Set Time.zone default to the specified zone and make Active Record auto-convert to this zone.
    # Run "rake -D time" for a list of tasks for finding time zone names. Default is UTC.
    # config.time_zone = 'Central Time (US & Canada)'

    # The default locale is :en and all translations from config/locales/*.rb,yml are auto loaded.
    # config.i18n.load_path += Dir[Rails.root.join('my', 'locales', '*.{rb,yml}').to_s]
    # config.i18n.default_locale = :de
    config.paths.add File.join('app', 'api'), glob: File.join('**', '*.rb')
    config.autoload_paths += Dir[Rails.root.join('app', 'api', '*')]
  end
end

routes.rb

GrapeTest::Application.routes.draw do
  mount GrapeTestAPI::API => '/'
end