We present two tools that make students more productive during various object-oriented design activities. The first one, Trace Modeler, is a smart UML sequence diagram editor that helps students understand and apply responsibility-driven design. The second tool, Trace4J, is used to record and process the execution of a java program. Both tools are complementary. Students use Trace4J to produce focused sequence diagrams for (part of) a program's execution. Trace Modeler's support for huge diagrams lets them navigate and understand the large results in the initial stages of their processing experiments.