What is a key restriction when consuming REST API methods?

The correct answer reflects the understanding that REST APIs should typically adhere to specific standards and specifications to ensure broader compatibility and usability, one of which is the Swagger specification. Swagger, now known as OpenAPI Specification, provides a standard framework for describing the services a REST API offers, including the endpoints, methods, parameters, request and response formats, and other useful metadata. This adherence helps facilitate automatic documentation generation, client library generation, and clear communication about how to interact with the API.

Understanding this context is crucial for developers working with APIs, as following standards can simplify integration processes and client-side development. It signifies that although REST APIs do not inherently have to comply with the Swagger specification, conforming to it can enhance the usability and standardization of the API, thereby benefiting developers.

The other choices do not represent key restrictions inherent to REST API methods. Many REST APIs can be created without being publicly accessible, can implement various authentication methods, and do not need to call or support SOAP methods, which is an entirely different web service protocol. Thus, the focus on the importance of adhering to the Swagger specification underscores a best practice rather than a strict limitation when consuming REST APIs.