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="BattleAxe.bmp|8185" />
  </query-continue>
  <query>
    <allfileusages>
      <f ns="6" title="File:Backpack.png" />
      <f ns="6" title="File:Bake kitsune.jpg" />
      <f ns="6" title="File:BarbedSpear 01.bmp" />
      <f ns="6" title="File:BarbedSpear 02.bmp" />
      <f ns="6" title="File:Barbed runic sewing kit.gif" />
      <f ns="6" title="File:BarberShop Narrowhaven.jpg" />
      <f ns="6" title="File:Bardiche.bmp" />
      <f ns="6" title="File:Bardiche.png" />
      <f ns="6" title="File:Bardiche 01.bmp" />
      <f ns="6" title="File:Bardiche 02.bmp" />
    </allfileusages>
  </query>
</api>