Since the PSD2 came into force, additional knowledge of the XS2A protocol is required to establish the multi-bank capability of portals or applications. Currently, this knowledge can be drawn primarily from the Berlin Group specification. In Germany, the FinTS protocol can also be used to access all accounts that are not regulated by the PSD2. Due to the degrees of freedom allowed by the Berlin Group specification, it is not sufficient to implement the XS2A protocol only once. The different variants must be taken into account. Thus the make-or-buy question quickly arises.
If the decision is in favour of buying a solution, the TRAVIC-Payment-Client-API by PPI AG is an excellent choice.