Numerous design decisions are made while developing software systems, which influence the architecture of these systems as well as following decisions. A number of decision management tools already exist for capturing, documenting, and maintaining design decisions, but also for guiding developers by proposing potential subsequent design issues. In model-based software development, many decisions directly affect the structural and behavioral models used to describe and develop a software system and its architecture. However, these decisions are typically not connected to the models created during the development process. In this report, we propose an integration of a decision management and a UML-based modeling tool, based on use cases we distill from a case study: the modeling tool shall show all decisions related to a model and allow its users to extend or update them; the decision management tool shall trigger the modeling tool to realize design decisions in the models. We define tool-independent concepts and architecture building blocks supporting these use cases and present how they can be implemented in the IBM Rational Software Modeler and Architectural Decision Knowledge Wiki. This seamless integration of formerly disconnected tools improves tool usability as well as decision maker productivity.