By default, only the received request and the transmitted response gets logged for API's build in API Connect. But in case we need to log intermediate messages we need to pass below HTTP header in request to log the debug messages.
Apim-Debug:true
But we cannot ask the external systems to sent this header in request, which is not involved in the functionality. How can we implement this debug logging? Is there any other way?
There is potentially no way presently and its suggested to send these intermediate responses to some logging facility. One can also create an intermediate API and use activity logging in that.
Refer to the below thread for further discussions: https://developer.ibm.com/answers/questions/457253/api-connect-analytics-logging.html