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="BREADBOARD_POWER_SUPPLY_MODULE.jpg" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1188" ns="6" title="File:B.png" />
      <page pageid="1503" ns="6" title="File:BL18 ECG Maven-01.jpg" />
      <page pageid="1502" ns="6" title="File:BL18 ECG Maven hardware.jpg" />
      <page pageid="221" ns="6" title="File:BLE shield.jpg" />
      <page pageid="222" ns="6" title="File:BLE shield1.jpg" />
      <page pageid="223" ns="6" title="File:BLE shield2.jpg" />
      <page pageid="224" ns="6" title="File:BLE shield3.jpg" />
      <page pageid="225" ns="6" title="File:BLE shield4.jpg" />
      <page pageid="226" ns="6" title="File:BLE shield5.jpg" />
      <page pageid="346" ns="6" title="File:BMP085.jpg" />
    </pages>
  </query>
</api>