I think I read somewhere you have to add an annotation to your AbstractActionPipelineProcessor "@Publish (JBossWSWebserviceContractPublisher.class )" to publish a contract.
Thanks for your answer (I haven't tested it though) but I found out that it was possible to generate WSDL files for my services based upon XML schemas (by setting the 'inXsd', 'outXsd' and 'faultXsd' attributes of the services in 'jboss-esb.xml') and I will use this approach instead.
If you are talking about EBWS then you are correct, you can create a contract based on your inXSD. Keep in mind that defining those parameters implicitly activate validation. This can be deactivated by setting validate="false".
Here an example for defining your EBWS.
mep="RequestResponse" outXsd="yourOut.xsd" validate="true" webservice="true">
To check if it works, just type http://localhost:8080/contract to see the contract of your EBWS.