We describe CAT, a toolkit supporting the analysis of communication-centric applications, i.e., applications consisting of ensembles of interacting services. Services are modelled in CAT as contract automata and communication safety is defined in terms of agreement properties. With the help of a simple (albeit non trivial) example, we demonstrate how CAT can (i) verify agreement properties, (ii) synthesise an orchestrator enforcing communication safety, (iii) detect misbehaving services, and (iv) check when the services form a choreography. The use of mixed-integer linear programming is a distinguished characteristic of CAT that allows us to verify context-sensitive properties of agreement.