Which pieces of information to get:

wikitext

The expanded wikitext.

categories

Any categories present in the input that are not represented in the wikitext output.

properties

Page properties defined by expanded magic words in the wikitext.

volatile

Whether the output is volatile and should not be reused elsewhere within the page.

ttl

The maximum time after which caches of the result should be invalidated.

parsetree

The XML parse tree of the input.

Note that if no values are selected, the result will contain the wikitext, but the output will be in a deprecated format.