The Swagger specification requires a host parameter given for each definition. Since each Marketo instance has a different hostname, in order to properly leverage tools like swagger-codegen, the host needs to be customized for each definition file. You can use the forms above to download a customized definition with your unique hostname by entering your Munchkin ID in one of the forms given. You can obtain your subscription’s Munchkin ID by going to your Admin->Munchkin menu in the “Munchkin Account ID” field, or from the first part of your Marketo REST API host subdomain: https://{Munchkin ID}.mktorest.com