\assert($variable instanceof SomeClass);

After installing this plugin code above will start displaying following error:

Required parameter '$description' missing

This is simply just not true.
Code above is completely valid, and second argument of assert function is completely optional
PHP documentation states:

if no description is provided, a default description equal to the source code for the invocation of assert() is provided. 

Source:
https://www.php.net/manual/en/function.assert.php#refsect1-function.assert-parameters