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>
    <allimages gaicontinue="0a-esp8285_datasheet_en_V1.4.pdf" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1344" ns="6" title="File:01.73.02.0101 Sonoff DEV Dimension.pdf" />
      <page pageid="1345" ns="6" title="File:01.73.02.0101 Sonoff DEV Schematic.pdf" />
      <page pageid="1346" ns="6" title="File:01.73.02.0101 Sonoff DEV VIEW.pdf" />
      <page pageid="1690" ns="6" title="File:0A-ESP8266 Specifications v4.1.pdf" />
      <page pageid="1408" ns="6" title="File:0A-ESP8285 Datasheet CN.pdf" />
      <page pageid="1409" ns="6" title="File:0A-ESP8285 Datasheet EN.pdf" />
      <page pageid="1397" ns="6" title="File:0a-esp8266ex datasheet en.pdf" />
      <page pageid="1588" ns="6" title="File:0a-esp8285 datasheet cn.pdf" />
      <page pageid="1688" ns="6" title="File:0a-esp8285 datasheet cn V1.4.pdf" />
      <page pageid="1587" ns="6" title="File:0a-esp8285 datasheet en.pdf" />
    </pages>
  </query>
</api>