Is there an API instead of password/OTP screen integration?

No. Swisscom requires you to integrate the password/OTP screen only as an iFrame so that an external person knows it comes from Swisscom. Your added value is that you can use standard browser functions, which Swisscom publishes in its website links. This is by Chapter 4 of our terms of use. You can find more information on the iFrame integration on our GitHub: https://github.com/SwisscomTrustServices/AIS/wiki/SAS-Documentation