Enter a fully qualified URL (http://host.com/) to fetch using "Accept: application/xrds+xml"
(this should return a valid XDRS document)

Result:
<?xml version="1.0" encoding="UTF-8"?>
  <XRDS xmlns="xri://$xrds">
      <XRD xml:id="oauth" xmlns:simple="http://xrds-simple.net/core/1.0" xmlns="xri://$XRD*($v*2.0)" version="2.0">
        <Type>xri://$xrds*simple</Type>
        <Expires>2010-10-08T04:27:21Z</Expires>
        <Service priority="10">
          <Type>http://oauth.net/core/1.0/endpoint/request</Type>
          <Type>http://oauth.net/core/1.0/parameters/auth-header</Type>
          <Type>http://oauth.net/core/1.0/parameters/uri-query</Type>
          <Type>http://oauth.net/core/1.0/signature/PLAINTEXT</Type>
          <URI>http://www.partuza.nl/oauth/request_token</URI>
        </Service>
        <Service priority="10">
          <Type>http://oauth.net/core/1.0/endpoint/authorize</Type>
          <Type>http://oauth.net/core/1.0/parameters/uri-query</Type>
          <URI>http://www.partuza.nl/oauth/authorize</URI>
        </Service>
        <Service priority="10">
          <Type>http://oauth.net/core/1.0/endpoint/access</Type>
          <Type>http://oauth.net/core/1.0/parameters/auth-header</Type>
          <Type>http://oauth.net/core/1.0/parameters/uri-query</Type>
          <Type>http://oauth.net/core/1.0/signature/PLAINTEXT</Type>
          <URI>http://www.partuza.nl/oauth/access_token</URI>
        </Service>
        <Service priority="10">
          <Type>http://oauth.net/core/1.0/endpoint/resource</Type>
          <Type>http://oauth.net/core/1.0/parameters/auth-header</Type>
          <Type>http://oauth.net/core/1.0/parameters/uri-query</Type>
          <Type>http://oauth.net/core/1.0/signature/HMAC-SHA1</Type>
        </Service>
        <Service priority="10">
          <Type>http://oauth.net/discovery/1.0/consumer-identity/static</Type>
          <LocalID>0685bd9184jfhq22</LocalID>
        </Service>
      </XRD>
      <XRD xmlns:simple="http://xrds-simple.net/core/1.0" xmlns="xri://$XRD*($v*2.0)" version="2.0">
          <Type>xri://$xrds*simple</Type>
          <Expires>2010-10-08T04:27:21Z</Expires>
          <Service priority="0">
            <Type>http://specs.openid.net/auth/2.0/signon</Type>
            <Type>http://openid.net/signon/1.1</Type>
            <URI>http://www.partuza.nl/openid/auth</URI>
          </Service>
          <Service>
            <Type>http://portablecontacts.net/spec/1.0</Type>
            <Type>http://ns.opensocial.org/people/0.8</Type>
            <URI>http://modules.partuza.nl/social/rest/people</URI>
          </Service>
          <Service>
            <Type>http://ns.opensocial.org/activities/0.8</Type>
            <URI>http://modules.partuza.nl/social/rest/activities</URI>
          </Service>
          <Service>
            <Type>http://ns.opensocial.org/appdata/0.8</Type>
            <URI>http://modules.partuza.nl/social/rest/activities</URI>
          </Service>
          <Service>
            <Type>http://ns.opensocial.org/messages/0.8</Type>
            <URI>http://modules.partuza.nl/social/rest/messages</URI>
          </Service>
          <Service>
            <Type>http://ns.opensocial.org/rpc/0.8</Type>
            <URI>http://modules.partuza.nl/social/rpc</URI>
          </Service>
          <Service priority="10">
            <Type>http://oauth.net/discovery/1.0</Type>
            <URI>#oauth</URI>
          </Service>
      </XRD>
  </XRDS>

source code of this file