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>
    <alltransclusions gatcontinue="BattleTier|266" />
  </query-continue>
  <query>
    <pages>
      <page pageid="86" ns="10000" title="Tank:G06 PzII" />
      <page pageid="88" ns="10000" title="Tank:G102 Pz III" />
      <page pageid="89" ns="10000" title="Tank:G25 PzII Luchs" />
      <page pageid="91" ns="10000" title="Tank:G26 VK1602" />
      <page pageid="113" ns="10000" title="Tank:G21 PanzerJager I" />
      <page pageid="119" ns="10000" title="Tank:R11 MS-1" />
      <page pageid="124" ns="10000" title="Tank:R12 A-20" />
      <page pageid="262" ns="10000" title="Tank:G20 Marder II" />
      <page pageid="94605" ns="10004" title="Ship:Matchmaking" />
      <page pageid="117177" ns="10004" title="Ship:Update 13.5" />
    </pages>
  </query>
</api>