The ANSIBLE_DEBUG environmental variable can be used to return debugging information. Here is how to temporarily enable debugging.

export ANSIBLE_DEBUG=True

When issuing a command, such as the ad-hoc ansible command or the ansible-playbook command, something like this should be included in the output.

debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 58: Applying options for *
debug1: auto-mux: Trying existing master
debug2: fd 3 setting O_NONBLOCK
debug2: mux_client_hello_exchange: master version 4
debug3: mux_client_forwards: request forwardings: 0 local, 0 remote
debug3: mux_client_request_session: entering
debug3: mux_client_request_alive: entering
debug3: mux_client_request_alive: done pid = 24663
debug3: mux_client_request_session: session request sent
debug1: mux_client_request_session: master session id: 2
debug3: mux_client_read_packet: read header failed: Broken pipe