I hate the ISTP one, it focuses too much on being mechanically inclined, I can't relate.
Existing ones are already peoples observations. Even if we were to create type descriptions like you say it wouldn't prevent the forer effect from happening. You're just using that to discredit functions anyways. Functions aren't vague and inconsistent like zodiac signs. Most type descriptions I can't relate to and most functions don't resonate much with me. Most people I would think feel the same.Type descriptions should be based off studies where they are compared to other types in a way that differentiates them to reduce the Forer/Barnum effect.