For Partner Merchant Account only
For Active a Partner account (contact us)
Onboarding API is mainly for those third party merchant who already have their own merchant base but like to integrate our OpenAPI. In this way to onboard the merchants, we will directly deal with merchant instead by partner since u have onboarded the merchant information.
For all OpenAPI other than Onboarding API, you will also need to use "Onboarded Merchant Account" Developer Application to do with.