In global software development (GSD) projects, distributed teams collaborate to deliver high-quality software. Project managers need to control these development projects, which increasingly adopt agile practices. However, in a distributed project a major challenge is to keep all team members aware of recent changes of requirements and project status without providing too little or too much information for each role. In this paper we introduce a framework to define notification for development team members that allows a) measurement of notification effectiveness, efficiency, and cost; b) formalizing key communication in an agile environment; and c) providing a method and a tool to implement communication support. We illustrate, with an example scenario from an industry background, the concept and report results from an initial empirical evaluation. From the evaluation it follows that the concept allows determining and increasing the effectiveness and efficiency of key communication in ...