Recent research has emphasized the importance of reflection for students in intelligent learning environments. This study tries to investigate whether agent prompts, acting as scaffolding, can promote students' reflection when they act as tutor through teaching the agent tutee in a learning-by-teaching environment. Two types of agent prompts are contrasted in this research, both from the perspective of a tutee, and they differ in their specificity. Generic prompts are aiming at eliciting students' double-loop reflection on metacognitive strategies and beliefs. Specific prompts, on the other hand, are to encourage students' single-loop reflection on domain-related and task-specific skills and articulation of their explanatory responses. Our findings suggest that designers of intelligent learning environment should concentrate on fostering students to reflect on their metacognitive strategies and beliefs, and allow students to take responsibility for directing their own learning autonomy. (Contains 4 tables and 6 figures.)