A certified nursing assistant (CNA) provides healthcare services and assistance to patients in medical facilities, assisted living centers, or private homes. CNA agency jobs are those CNA positions found or placed through a mediating agency. You receive assignments from a staffing agency and fill the position for the length of the posting. Your responsibilities may vary depending on the details of each job placement. CNAs assist patients with daily activities, take and record vital signs, or help physicians and nurses as needed. In a private home or assisted living facility, your duties may sometimes include helping with cleaning or cooking tasks.