With the progress in several technologies, robots have been developed for educational support. However, these educational robots have a problem that children gradually lose their motivation for learning as they get used to interacting with the robots. To solve the problem of maintaining interest among children, the authors propose a new interaction method with the agent (user-generated agent: UGA) for an educational system with robots, in which children themselves design the contents of the agent. With the theme of introducing recommended books based on actual educational approaches, we construct a UGA system with an agent interposed between the child creator and the child listener, and conduct field research at an elementary school. The results reveal that the robot introduced books 17.9 times per day on average, the children took actions to pick up books after receiving introductions, and introduction methods with non-verbal expressions were effective. The UGA designer was not used much in the early stages of the research. The authors improved the UGA designer so that children designed four new items of content despite a short period. It is important to hide the name of the child who created the content in a method that allows children to design.