One popular approach to object design proposes to identify responsibilities from software contracts, apply a number of principles to assign them to objects, and finally construct an object interaction that realizes the contract. This three-step activity is currently a manual process that is time-consuming and error-prone, and is among the most challenging activities in object-oriented development. In this paper, we present a model transformation that partially automates this activity. Such a transformation is modularized in three stages. The first stage automatically transforms a software contract to a trace of state modification actions. In the second stage the designer manually extends the trace with design decisions. Finally, the extended trace is automatically transformed to an object interaction in the third stage. A prototype of the whole transformation was developed and successfully applied to a case study from the literature. Our technique allows the extraction of valuable information from software contracts, provides a bridge between analysis and design artifacts, and significantly reduces the effort; of interaction design.