I created a hello world action, could invoke it in the browser.
Invoking with curl and using the API key provided resulted in an error:
$ curl -u API-KEY -X POST https://us-south.functions.cloud.ibm.com/api/v1/namespaces/jps_LMI/actions/HelloWorld?blocking=true
{"code":"cd01b7ea690a0454ef05016daa917bd3","error":"The supplied authentication is invalid"}
Calling the unprotected request is working fine:
https://us-south.functions.cloud.ibm.com/api/v1/web/jps_LMI/default/HelloWorld.json