I just realized that the best way to grab the WSDL of a service is probably via HTTP OPTIONS rather than HTTP GET. OPTIONS was designed to return information which describes the interface to a service. From RFC 2616;
The OPTIONS method represents a request for information about the communication options available on the request/response chain identified by the Request-URI. This method allows the client to determine the options and/or requirements associated with a resource, or the capabilities of a server, without implying a resource action or initiating a resource retrieval.