Automation to add a tag to API imported contact

we use API to import contacts from another app, Everything seems running well and Infusionsoft can create new contact and update existing contact. But the problem is it doesn’t add any tag on those contact, so It can’t trigger any automation campaigns.
I know it is possible to add tag build-in on the API. Unfortunately, I don’t have access to the API. Is there any way I can automate adding tags to those contact using only Infusionsoft tools?

Does anyone know about this matter? I’m really stuck