Article 13 of the MLI modifies Article 5(4) of the OECD Model Tax Convention, which deals with a list of exceptions that do not constitute a Permanent Establishment. The rationale behind creating an exception list is that all activities mentioned in the list have a preparatory or auxiliary character that is not enough to establish a significant economic presence in another jurisdiction.

This episode is also available as a blog post: https://taxbeech.com/2021/06/29/complete-guide-on-article-13-of-mli/