How to document @throws in interface documentation

I'm writing a PHP library and I have a concern. I have something similar to the following in my interfaces:

<?php
/**
 * My interface
 *
 * ...
 */
interface MyInterface
{
    /**
     * This method does foo.
     *
     * @throws \RuntimeException If foo can't be done.
     */
    public function fooAndBar();
}
?>

Now, the @throwsentry isn't perfectly right, since an interface doesn't actually do anything, and is used purely to abstract implementation details. However, I've always used it because all my implementations of the interface thrown the exception when something goes wrong.

But another developer might write an implementation that can't fail (so it can't throw an exception), or he/she might want to use another exception class.

In this situation, how should I document @throws in interface declarations? Should it even be documented?