Spec at http://msdn.microsoft.com/ws/2004/03/ws-metadataexchange 

WS-MetadataExchange expands the existing Web services architecture to govern the transfer of metadata
, enabling endpoints to leverage other Web services specifications for secure, reliable, transacted message delivery.

sample code for retrieving policy from the spec ...

<s:Envelope ...>
  <s:Header ...>
    <wsa:Action>
        http://schemas.xmlsoap.org/ws/2004/03/mex/GetPolicy/Request
    </wsa:Action>
    <wsa:MessageID>xs:anyURI</wsa:MessageID> ?
    <wsa:ReplyTo>endpoint-reference</wsa:ReplyTo> ?
    <wsa:To>xs:anyURI</wsa:To>
    ..
  </s:Header>
  <s:Body ...>
    <wsx:GetPolicy ...>
      <wsx:TargetNamespace ...>xs:anyURI</wsx:TargetNamespace> ?
    </wsx:GetPolicy>
  </s:Body>
</s:Envelope>