Ability to access short answers and multiple choice answers via API

We are planning to use the Populi API to automatically grade certain assignments.  We can access essay content, but we are unable to access the student answers to the Test questions.  We would like the ability to access the answers and grade them via the API.  We can set an overall grade on the test submissions,  but the answers to the questions still show up in the 'to be graded' tab.