You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allfileusages gafcontinue="Bulbgraph.png|28" />
  </query-continue>
  <query>
    <pages>
      <page pageid="77" ns="0" title="CAD:Vector Based" />
      <page pageid="153" ns="0" title="PLUGIN:Block Extractor" />
      <page pageid="154" ns="0" title="PLUGIN:Bulk Block Fixer" />
      <page pageid="696" ns="0" title="HOWTO:Use Existing Drawing In Current Project" />
      <page pageid="837" ns="0" title="Application:Support Paths" />
    </pages>
  </query>
</api>