A validation tool is provided for a representational state transfer (REST) service. In one embodiment, a method for validating documentation of a REST service includes including detecting one or more messages for a REST service by a validator, wherein the one or more messages are intercepted for the REST service, translating documentation of the REST service, by the validator, into a representation of an automaton, and validating the one or more messages by the validator based on the automaton, wherein validation of the messages determines conformance of the REST service to the documentation of the REST service.