Requirements engineers need to understand and model different aspects of organizations and systems under construction, and may need to use different modeling notations. However, most modeling tools support only one (or at most a few notations), hindering requirements engineers from using the most appropriate notations for the particular modeling task. The RE-Tools is an open-source toolkit implemented using a UML Profile for StarUML, an open-source UML modeling tool. The toolkit supports many leading requirements modeling notations, including the NFR Framework, the i∗ Framework, KAOS, Problem Frames, and UML. Each of these notations may be used for modeling independent corresponding diagrams or together with non-functional requirements (NFRs). The toolkit also supports the original qualitative reasoning of the NFR Framework and augments with a quantitative one.