Is FormVlidationAction necessary for a form to be built?

Like, take the “utter_wrong_slot” action to get necessary info by asking and fill the slot with the text given next when the required slot is not filled

I’m a bit unsure what you’re asking. Could you clarify what you mean by “asking and fill the slot with the text given next when the required slot is not filled”?

If you’re asking if you really must have a validator in a form then no. Technically you can skip the validator in a form. I wouldn’t recommend this, but you don’t strictly need it.

“asking and fill the slot with the text given next when the required slot is not filled” means to collect info by asking if the “custom action” class didn’t wotk ( it’s an ocr function so it’s possible that some pieces might not be well-recognized ) whether I must have a validator in a form is also a question that I want to ask, thx I got it

or to say “asking and fill the slot with the text given next when the required slot is not filled” refers to

dispatcher.utter_message(response=“utter_wrong_arrival_station”)

this line