This paper presents a freely available, and flexible Wizard of Oz environment for rapid prototyping. The system is designed to investigate the required features of a dialog system using the commonly used Wizard of Oz approach. The idea is that the time consuming design of such a tool can be avoided by using the provided architecture. The developers can easily adapt the database and extend the tool to the individual needs of the targeted dialog system. The tool is designed as a client-server architecture and provides efficient input features and versatile output types including voice, or an avatar as visual output. Furthermore, a scenario, namely restaurant selection, is introduced in order to give an example application for a dialog system.