Ansible Task File Include and Variable issue

#####################
MAIN PLAYBOOK EXCERPT
#####################
    - include: tasks/configure-restart.yaml 
      vars:
        agent_state: present
        
#################
TASK FILE EXCERPT
#################

- name: Modify configuration
  lineinfile:
    dest: '{{ crazy.stat.path }}'
    line: 'some silly configuration line'
    state: '{{ agent_state }}'
  when: crazy.stat.exists
  
#####
ERROR
#####
fatal: [x.x.x.x] => One or more undefined variables: 'agent_state' is undefined