If you are developing with the Shiptheory API, you will need to create a regular Shiptheory account. Once registered, select the Free Trial, This gives you access to our API. Please note that partner companies that are using the API and are building a platform into it will require a partner tag from the email dev@shiptheory.com
Additionally, if you do not have a Carrier account yet but wish to test creating labels and tracking numbers, you can enable Shiptheory's Address Only Labels. From the settings page, set Generate Faux Tracking Numbers to Yes to have the API generate and return fake tracking numbers. For more information on this feature, see Address Only Labels.