XS2A Core is an interface that provides third-party providers access to client accounts managed by an Account Servicing Payment Service Provider (ASPSP) bank, as required by PSD2. It implements the core services defined by PSD2, including payment initiation, account information services, and confirmation on funds availability. XS2A Core is fully compliant with PSD2 standards and provides a secure interface for third parties to initiate payments, get account information, and check card balances for bank customers.