The capabilities available to your application from an instance of an on-premise Content Services are described in an AtomPub service document returned when calling the base URL. The service document contains information on the repository, the CMIS methods that can be called on it, and the parameters for those methods.
To retrieve the service document use the HTTP GET method with this URL: https://localhost:8080/alfresco/api/cmis/versions/1.1/atom/
The response body is an AtomPub XML document which describes the CMIS capabilities in a standard way. See the CMIS specification for more details.