You must add your public ssh key to the hosts:
use ssh-copy-id <ip> to copy directly from your ssh-agent (ssh-add -L)
Next you'll need avahi-daemon to be running on the server you're trying to reach (if using the hostname to connect through mDNS)
You can use the playbook for this:
ansible-playbook -i <ip>, playbooks/init.yml -K
Note: Comma is needed after Note: "all" must be defined in the hosts file
Running ansible:
# ping nodes
ansible all -m ping
ansible cluster_worker -m ping
# getting temp
ansible cluster -m shell -a '/usr/bin/vcgencmd measure_temp'