There is a simple way to programmatically fetch help documentation for system functions based on what text is stored in the xpo-files.
If you run this:
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static void getSystemDocumentation_Job(Args _args)
{
    ;
    info(Web::stripHTML(TreeNode::findNode(@"\System Documentation\Functions\abs").AOTgetSource(), true, true));
}
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then an infolog will appear:
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Information:

Abs
 [HEADER]

Returns the absolute value of arg.

Examples
Abs(-100.0) returns the value '100.0'.

Abs(30.56) returns the value '30.56'.
static void Job_Examples_22885_1_abs(Args _args)
{
  real r1;
  real r2;
  ;

  r1 = abs(-3.14);
  r2 = abs(3.14);
  if (r1 == r2)
  {
    print "abs of values are the same";
    pause;
  }
}

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Unfortunately, special symbols like ‘>’ are converted to something like ‘&lt’, but still this is a way to understand what the kernel function does.