grape-apidoc

# Gemfile
group :development do # most common use env is env=development
  gem 'grape-apidoc'
end

# Rakefile
begin
  require 'grape/apidoc'
  Grape::Apidoc::RakeTask.new(:apidoc, root_api_class: Grape::App) # point it to the top-level API class
rescue LoadError
  nil # so it does not fail in non-development environment
end