The formulation of the Open API Framework is one of the seven initiatives announced by the HKMA in 2017 to prepare Hong Kong to move into a new era of Smart Banking. Open API allows financial institutions to open up their internal IT systems and data for programmatic access by third-party service providers (TSPs) or their counterparts in an open and documented manner.
For details, please read:
https://www.hkma.gov.hk/eng/key-functions/international-financial-centre/fintech/open-application-programming-interface-api-for-the-banking-sector/