Ansible playbooks are as idempotent as bash scripts. You need to include checks when writing them so they actually are idempotent, just like with bash script,

Ansible playbooks are as idempotent as bash scripts. You need to include checks when writing them so they actually are idempotent, just like with bash script, and they happily leak idempotency-breaking details like "restarting a service" works only if a) service currently runs b) because "restart" is a command, not expected state of "the service was restarted and is now running