What must occur before using a service through the IBM Watson SDK?

Before utilizing a service through the IBM Watson SDK, it is essential to create a new instance of the service in Bluemix. This process involves provisioning a specific instance of the Watson service that you intend to use, which allows you to interact with the API and access its functionalities. Each Watson service, such as Watson Assistant or Watson Natural Language Processing, requires a dedicated instance in order to provide a unique endpoint and associated credentials necessary for your application to communicate with it effectively.

Creating an instance ensures that you have a segregated environment where you can manage the service's configuration and usage limits according to your needs. Following this step, you would typically gain access to environment variables containing API keys and URLs, which can be utilized in your application setup using the SDK.

While having sufficient credit in your IBM Bluemix account may be a requirement for resource management, it is not a prerequisite specifically related to the SDK usage. Similarly, while other environment variables configuration may be necessary after the service is created, the foundational step that enables the service access is indeed the creation of the service instance itself.