Quality of Service (QoS) analysis and prediction for Web service compositions is an important and challenging issue in distributed computing. In existing work, QoS for service compositions is either calculated based on constant QoS values or simulated based on probabilistic QoS distributions of component services. Simulation method is time consuming and can not be used in real-time applications for dynamic Web service compositions. Experimental results in  show that our proposed QoS calculation approach significantly improves the efficiency in QoS estimation when the QoS of component Web services are probability distributions. In this paper, we present a tool QoSDIST to analyze the QoS for Web service compositions based on our proposed QoS calculation method in . QoSDIST does not put any constraints on the modeling of the QoS of component Web services, i.e., the QoS of a component Web service can be in single value, discrete values with frequencies, standard statistical distribution, or any general distribution regardless of its shape.