Ansible return values

- name: Updating current Windows Installation with all available Updates for the OS
  win_updates:
    category_names: ['SecurityUpdates','CriticalUpdates','UpdateRollups','ServicePacks','Application','Connectors','DefinitionUpdates','FeaturePacks','Tools','Updates']
  register: reboot_hint

- name: Status of Updates
  debug: var=reboot_hint.stdout.reboot_required
---------------------------------------------------  
ok: [192.168.0.168] => {
    "reboot_hint.stdout.reboot_required": "VARIABLE IS NOT DEFINED!"
}

#########################################################################

ok: [192.168.0.168] => { "reboot_hint": { "changed": false, "found_update_count": 0, "installed_update_count": 0, "reboot_required": true, "updates": {} } }