XCAP (RFC 4825) is a protocol on top of HTTP allowing a client (usually built within a SIP user agent) to manipulate the content of XML documents stored in a server. These documents represent per user buddy list, presence authorization policy, media content (i.e. user avatar) and other kind of features.Ruby XCAPClient library implements the XCAP protocol in client side, allowing the application to get, store, modify and delete XML documents (totally or partially) in the server.