A method, system and program product for overriding existing functionality provided in an application programming interface (API) for a local protocol implementation is provided. The method includes providing an API for a local protocol implementation having a raw interface function that can be invoked by a client application to override existing functionality provided in the API. The method further includes defining for the raw interface function an array of pre-formed payload elements to be included for creating a customized protocol request message for requesting a protocol service from a server application using a remote protocol implementation different than the local protocol implementation, populating data for each element in the array defined, and invoking the raw interface function, which takes as input the array defined and inserts them, in order, behind a protocol message header of the protocol request message and sends the customized protocol request message to the server application.