TuTalk supports the rapid development of dialogue agents for learning applications. It enables an experimenter to create a dialogue agent with either minimal or no programming and provides the infrastructure needed for testing hypotheses about dialogue. Our main goals in developing this tool were to provide 1) an authoring interface and language for setting up the domain knowledge and resources needed to support the agent and 2) a plug-and-play type of system that facilitates the integration of new modules and experimentation with different core modules. In this paper we describe the authoring tool and the usability studies that have shaped its design, the dialogue that is supported and features of the authoring language and their usage history.