VarTag
Is used for processing @var, @property and @param tags.
/**
 * @property Bar $value  Some Bar thing to use
 */
class Foo
{
}
For @property and @param tags it’s better to use a wrapper MultiTag, to group them in properies and params arrays (see MultiTag for an example).
All these three tags are already included in PhpDocumentor::tags(), but still here’s a simple example.
$doc = (new ReflectionClass('Foo'))->getDocComment();
$customTags = [new VarTag('property', $fqsenConvertor, ['some-more' => 'data'])];
$notations = getNotations($doc, $customTags);
var_export($notations);
Result:
[
    'property' => [
        'type' => 'Zoo\Baz\Bar',
        'name' => 'value',
        'some-more' => 'data',
        'description' => 'Some Bar thing to use'
    ]
]
$fqsenConvertor was used to expand property type to namespaced name. Also, as you see, additional custom data can be added to result notations.