WSDL should have both request and response structures.
eg:
<operation name="sayHello">
<soap:operation soapAction="sayHello"/>
<input>
<soap:body
encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"
namespace="urn:examples:helloservice"
use="encoded"/>
</input>
<output>
<soap:body
encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"
namespace="urn:examples:helloservice"
use="encoded"/>
</output>
In the SOA Tools, is there an add service call option? if so see attached snapshots.
Use the Add Service call, select the operation and target, and use the tabs Step Properties to see the structure of response message, and checkpoint to add your XPATH based validation of response.