unleash.unleash/docs/sdks/ruby.md

id	title
ruby_sdk	Ruby SDK

You will need your API URL and your API token in order to connect the Client SDK to you Unleash instance. You can find this information in the “Admin” section Unleash management UI. Read more

    require 'unleash'

    @unleash = Unleash::Client.new(
      url: '<API url>',
      app_name: 'simple-test',
      custom_http_headers = {'Authorization': '<API token>'},
    )

Read more at github.com/Unleash/unleash-client-ruby