Object IDs, SIS IDs, and special IDs. Throughout the API, objects are referenced by internal IDs. You can also reference objects by SIS ID, by prepending the SIS ID with the name of the SIS field, like sis_course_id:. For instance, to retrieve the list of assignments for a course with SIS ID of A1234: /api/v1/courses/sis_course_id:A1234/assignments