Which of the following is a fundamental aspect of consuming a REST API in OutSystems?

Consuming a REST API in OutSystems indeed has a fundamental requirement that aligns with being compliant with Swagger specifications. Swagger, now part of the OpenAPI Initiative, is widely used to describe the functionalities of RESTful APIs in a machine-readable format. By complying with these specifications, APIs provide a clear, standardized way to document their endpoints, data formats, authentication methods, and response types. This allows developers to easily understand how to interact with the API, making it easier to generate client code and perform integrations within OutSystems applications.

While other options mention important features, they do not represent fundamental requirements for consuming REST APIs in OutSystems. CORS policies are crucial for managing cross-origin requests, but they are not a core requirement for consuming an API. User authentication often enhances security and access control but is not inherently required for the basic use of a REST API, as there are many public APIs that do not require this. SOAP support is specific to SOAP APIs, which are distinct from REST APIs, and thus does not apply when discussing RESTful interactions.