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="Planned_section.png|4006" />
  </query-continue>
  <query>
    <allfileusages>
      <f fromid="1248" ns="6" title="Файл:Crystal Clear action run.png" />
      <f fromid="1276" ns="6" title="Файл:Crystal Clear action run.png" />
      <f fromid="3989" ns="6" title="Файл:Crystal Clear app kedit.png" />
      <f fromid="4037" ns="6" title="Файл:Mail mark junk red.png" />
      <f fromid="4238" ns="6" title="Файл:Minus.png" />
      <f fromid="4031" ns="6" title="Файл:Nuvola apps important yellow.png" />
      <f fromid="4236" ns="6" title="Файл:Ok.png" />
      <f fromid="4042" ns="6" title="Файл:Pictogram voting oppose.png" />
      <f fromid="4043" ns="6" title="Файл:Pictogram voting oppose.png" />
      <f fromid="4039" ns="6" title="Файл:Pictogram voting support.png" />
    </allfileusages>
  </query>
</api>