I want to create a creature that gives you poisons when it attacks you

I hope its fine that I created this forum, the other one was inactive and I did not get a response even after waiting for a few days. I want my mod to be done quite soon because of reasons.

So I found another forum thing talking about this topic and did as a person there told me too, but he/she did not explain good enouth for my small brain to understand how to make the game filter out all mobs except the one I created. When I tried it did not work.

My code bassicly: 

(global trigger) Entity attacked

If Source entity tagged in entity tags as "grankfars_buzzy_bugs:mosquito"

do Add potion POISON with level 1 for 60 ticks to Event/target entity

What should I do different?

Original conversation: https://mcreator.net/forum/67634/when-entity-attacks-entity