Multiparty session types constitute a method to automatically detect violations of protocol implementations relative to specifications. But, when a violation is detected, does it symptomise a bug in the implementation or in the specification? This paper presents dcj-lint: an analysis tool to detect bugs in protocol specifications, based on multiparty session types. By leveraging a custom-built temporal logic model checker, dcj-lint can be used to efficiently perform: (1) generic sanity checks, and (2) protocol-specific property analyses. In our benchmarks, dcj-lint outperforms an existing state-of-the-art model checker (up to 61x faster).