Most of the command-line clients support passing --debug before a subcommand. For example, with Keystone or Nova, it could look like this:

$ keystone --debug service-list
$ nova --debug list

Note that --debug is put before the subcommand being executed. Using the debug option like this is helpful because it will show curl commands for each of the API calls that are being made from the command-line client to the API endpoints. Hosts and ports are included in this, so if your command-line client has trouble connecting to the endpoint, you can use the debug option to get more detail. If you need to see what information is being sent from or returned to the command line, the debug option will show those details.