While multimodal systems are an active research field, there is no agreed-upon set of multimodal interaction parameters, which would allow to quantify the performance of such systems and their underlying modules, and would therefor be necessary for a systematic evaluation. In this paper we propose an extension to established parameters describing the interaction with spoken dialog systems [Möller 2005] in order to be used for multimodal systems. Focussing on the evaluation of a multimodal system, three usage scenarios for these parameters are given.