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="BR-MinasGerais|2149" />
  </query-continue>
  <query>
    <pages>
      <page pageid="2144" ns="0" title="Marshal Deodoro Class Battleship (1898)" />
      <page pageid="2145" ns="0" title="Marshal Deodoro (1898)" />
      <page pageid="2146" ns="0" title="Marshal Floriano (1899)" />
      <page pageid="2147" ns="0" title="Minas Gerais Class Battleship (1908)" />
      <page pageid="2148" ns="0" title="Minas Gerais (1908)" />
      <page pageid="9048" ns="10" title="Template:Footer Marshal Deodoro Class Battleship (1898)" />
    </pages>
  </query>
</api>