Item Rule to validate Item Description Length not triggered

Summary

Validate Item Description entered by the user to prevent exceeding a given length.

Content

Hi,

I have a requirement to validate the length of the item descriptions that are entered by the user.
Ideally the validation should occur regardless the Item Class used, if it is via NIR, Change request or direct update.

I assumed this would be easily to achieve by creating a new Item Rule, but somehow the rule does not get triggered on Save or Submit a new item or update of an existing item.

I created a new Rule Set using the following details:

Type: