Gameful design, including gamification, has proved helpful in increasing user engagement while using interactive systems in various contexts and domains including professional, leisure, healthcare…. The use of game-related elements correspond to the addition of new goals and tasks for the user to perform. In the context of work, users' goals and tasks strongly relate to the users' missions and objectives in the work organization. As part of the tasks may be automated at design time, allocation of tasks between the user and the interactive systems supporting these users' tasks has to be carefully analyzed, elicited and designed, so that the user can reach the objectives and goals assigned with adequate performance and acceptable error rate. This paper argues that the gameful design of interactive systems in the workplace requires precisely identifying and describing automation in work tasks, as well as users' tasks with the game elements. For that purpose, the paper presents a task models based approach that enables to analyze and design automation while applying gameful design. The paper presents an illustration of the approach using the example of an operator performing a monitoring task.