xmlrpc is a command-line interface to the XML-RPC protocol. The spec for XML-RPC is here: http://www.xmlrpc.com/spec. It's a remote procedure call protocol using XML for both the request and the response. This program lets you give the request parameters as command-line arguments, formats them up as XML, sends them to the server, and shows you the response.
See the manual entry for more details.
ACME Labs / Software / xmlrpc