Aspect-oriented programming introduces new challenges for software testing. In particular the pointcut descriptor (PCD) requires particular attention from testers. The PCD describes the set of joinpoints where the advices are woven. In this paper we present a tool, AjMutator, for the mutation analysis of PCDs. AjMutator implements several mutation operators that introduce faults in the PCDs to generate a set of mutants. AjMutator classifies the mutants according to the set of joinpoints they match compared to the set of joinpoints matched by the initial PCD. An interesting result is that this automatic classification can identify equivalent mutants for a particular class of PCDs. AjMutator can also run a set of test cases on the mutants to give a mutation score. We have applied AjMutator on two systems to show that this tool is suitable for the mutation analysis of PCDs on large AspectJ systems.