Provided is an API invoker of performing an onboarding. The API invoker includes a transceiver and a processor coupled with the transceiver and configured to obtain, from a service provider, onboarding information including an onboarding credential and information of a CAPIF core function, establish a secure session with the CAPIF core function based on the onboarding information and control the transceiver to transmit, to the CAPIF core function, an onboard API invoker request message along with the onboarding credential and to receive an onboard API invoker response message based on a result of a validating the onboarding credential at the CAPIF core function.