The SAIBA framework proposes two interface languages to represent separately an intelligent agent’s communicative functions (or intents) and the multimodal behavior determining how the functions are accomplished with a particular multimodal realization. For the functional level, the Function Markup Language (FML) has been proposed. In this paper we summarize the current status of FML as discussed by the SAIBA community, we underline the major issues that need to be addressed to obtain a unified FML specification, we suggest further issues that we identified and we propose a new unified FML specification that addresses many of these issues.