AmazonMarketplaceWebService.registration_url

[pismopomoyka]

I am sorry for it. I want to ask a question but don't know how. So i have used issues.
I have found VERY interesting code for my:

module ActiveFulfillment
      class AmazonMarketplaceWebService < Service
        ..........
        def registration_url(options)
          opts = {
            "returnPathAndParameters" => options["returnPathAndParameters"],
            "id" => @options[:app_id],
            "AWSAccessKeyId" => @options[:login],
            "SignatureMethod" => "Hmac#{SIGNATURE_METHOD}",
            "SignatureVersion" => SIGNATURE_VERSION
          }
          signature = sign(:get, REGISTRATION_URI, opts)
          "#{REGISTRATION_URI.to_s}?#{build_query(opts)}&Signature=#{signature}"
        end
        .........
end

Anybody can tell what is it "id" value? How can i get this value? I was looking for Amazon documentations about this MWS API but has found nothing.
I develop application and i want use this API for getting AmazonAuthToken.