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 afcontinue="CBREM_GUI.png" />
  </query-continue>
  <query>
    <allfileusages>
      <f ns="6" title="File:BCAL LED Pulser.png" />
      <f ns="6" title="File:BCAL environmental sensors.png" />
      <f ns="6" title="File:BCAL voltages.png" />
      <f ns="6" title="File:Base lockup RootSpy.png" />
      <f ns="6" title="File:Base lockup V.png" />
      <f ns="6" title="File:Base lockup channel.png" />
      <f ns="6" title="File:Base lockup scalers.png" />
      <f ns="6" title="File:Bcal css.png" />
      <f ns="6" title="File:Beam Energy.png" />
      <f ns="6" title="File:Beam line jack.jpg" />
    </allfileusages>
  </query>
</api>