I used soap-gateway, before Nick's revamping, in a couple of SOAP application, and so my responses are limited to the soap-gateway package only.
* Does the SOAP Gateway package support feeding in a WSDL and getting a TCL API to access the web service?
No. soap-gateway provides an infrastructure for building server side services, but I had to create the client side procs.
I played a bit with tsoap and it look very promising, even if at times I encountered some problem that I didn't have the time to debug.
The client procs already provide the API to call a web service: not sure of understanding what do you mean with the idea of using the WSDL.
* Does it have error handling built in.
Yes, at least the original William's package.
* Is there an easy way to make a Tcl procedure into a SOAP web service using the SOAP Gateway?
Yes, this is exactly the package's scope. You can look at the sample services provided to get an idea.
