Systems-of-Systems (SoS) result from associating independent, complex systems for fulfilling given missions. In particular, SoS require software architectures that can cope with their dynamic, critical nature. Selecting adequate Architecture Description Languages (ADLs) for representing such architectures contributes for a better communication, analysis, and evolution of these systems. Nonetheless, a consensus on which characteristics are important for describing SoS is not available yet. In this context, the main contribution of this study is the identification of the main features to be provided by ADLs for describing SoS software architectures. In the light of these features, we assessed some existing ADLs that have been used for this task and we noticed that they still miss some of the identified features. With this set of features, we intend to contribute to the SoS field with directions for making ADLs more suitable for the description of SoS software architectures.