Identity APIs allow you to identify and authenticate your end users.
OP Identity Service Broker is OP's replacement for TUPAS. It implements Strong Customer Authentication (SCA) and allows you to make use of all Finnish Strong Customer Credentials - including Mobile ID and bank credentials.
When you want to adopt OP Identity Service Provider in production, contact your local bank.
Note - Identity APIs are independent API products. Authentication and authorization for other API products use their own, separate flows (see e.g. Authorization Code Grant).