A Cyber-Physical System (CPS) comprises the integration of computation, software, networking, and physical processes. Consequently, CPS models extend traditional embedded system models with an increased support for hybrid and heterogeneous models, networking, time synchronization, and especially interoperability. To assist engineers in designing CPSs, we have developed aDSL, a Domain-Specific Language (DSL) that comes with fully-automated tool support and is tailored to interoperability of CPS. The aDSL tool support includes: (i) interactive model description with input validation; (ii) the computation of possible operation modes of subsystems and parts; and, (iii) checking the adherence to requirements for various design alternatives and finding the Pareto optimal designs given these requirements. Moreover, aDSL generates intuitive visualizations throughout the toolchain which help design engineers to better understand the implications of design decisions and communicate them to stakeholders. aDSL has been applied to an agricultural tractor-trailer system case study in which aDSL quickly evaluated 48 designs and rendered all the visualizations of the results.