WCF UriTemplate with large query strings

I'm working with a rather large query string(~30+ parameters) and am trying to pass them to a WCF service I've setup.

I've run into a few issues specifically with the UriTemplate field. This service is setup to access a third party Api, so the query string may or may not contain all parameters. I'm curious if the best approach is to build a query string and pass that to the WCF service or to pass each parameter(and in some cases String.Empty) individually.

I've currently tried to dynamically build up a query string, however have hit a wall with either a 403 error when I try to pass the entire string( "?prm1=val&prm2=val" ) into the uritemplate of "ApiTool.jsp{query}", or I hit an invalid uritemplate response due to the fact I don't have name/value pairs listed.