Ansible playbook that prints out all vars available during a play

debug_vars.yml

---
- name: dump all
  hosts: all
  gather_facts: false
  tasks:
    - name: debug | vars
      debug:
        var: vars

    - name: debug | environment
      debug:
        var: environment

    - name: debug | group_names
      debug:
        var: group_names

    - name: debug | groups
      debug:
        var: groups

    - name: debug | hostvars
      debug:
        var: hostvars