Same is the case with Siebel Tools, you require to consume it in Siebel tools which will result in creation of Web Service (which is nothing but the business service of Class: CSSWSOutboundDispatcher) and its corresponding Integration Objects.
So, the best way is to have a 3rd party tools to quickly verify the response from the other system. I have came across lot many tools which solve this purpose but my favourite is SOAPUI and I really find it very handy for this purpose.
This post is related to the very first step that you do while creating the outbound web service. I have picked one WSDL freely available on "http://www.webservicex.net/WS/default.aspx"
Now, lets see how to do it step by step:
1. Save the WSDL from the following link:
http://www.webservicex.net/CurrencyConvertor.asmx?WSDL

2. Get the SOAPUI tools, available at the below link:
http://www.soapui.org/
3. Open SOAPUI and go to File Menu -> Preferences and make sure following check boxes should be unchecked.

4. Now open the WSDL, that you have saved in Step 1. File Menu -> New SOAPUI Project OR Press Crtl N


5. You will see "Currency Converter" Web Service and its associated method in the left (Navigator) panel. Double click on "Request 1". It will bring up the SOAP Request / Response page in the right panel. The request XML will look like this:

6. Input the necessary values in FromCurrecny and ToCurrency tags of the request XML and hit the Go Button. For Eg:

7. Here is the response XML I received:

8. This confirms that WSDL is correct and working fine.
We will see in the next post, how to implement an Outboound WebService in Siebel.
Stay Tuned !!