# How to validate ansible variables - any condition you like, with proper error messages

**URL:** <https://forum.ansible.com/t/how-to-validate-ansible-variables-any-condition-you-like-with-proper-error-messages/46089>\
**Category:** Get Help\
**Tags:** variables, howto, ansible-core\
**Created:** [July 26, 2026, 7:49am UTC](https://forum.ansible.com/t/how-to-validate-ansible-variables-any-condition-you-like-with-proper-error-messages/46089 "2026-07-26T07:49:59Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![kks](https://sea1.discourse-cdn.com/ansible/user_avatar/forum.ansible.com/kks/32/10352_2.png) [@kks](https://forum.ansible.com/u/kks)\
**Post date:** [July 26, 2026, 7:49am UTC](https://forum.ansible.com/t/how-to-validate-ansible-variables-any-condition-you-like-with-proper-error-messages/46089/1 "2026-07-26T07:49:59Z")

</div>

There is a builtin action plugin to validate ansible variables (for the role)  
[`ansible.builtin.validate_argument_spec`](https://docs.ansible.com/projects/ansible/latest/collections/ansible/builtin/validate_argument_spec_module.html)

But this is sometimes very limited. It is not clear how to add condition like (0 \< a, a \> 100). It is impossible to add conditions to nested values for dict or list (or I do not know how to do that).

That is why I’ve created `capable.core212.validate_vars` - action plugin that validates ansible variables.

Main differences:

- Strict types - int, str and types that allow coercion - str\_int, str\_bool
- Custom validation conditions with **this** keyword
- `mutually_exclusive`, `required_together`, `required_one_of`, `required_if`, `required_by` but for ansible variables (not module arguments)

Let’s start with simpliest example - validate that int value is between 0 and 100

```yaml
- capable.core212.validate_vars:
    custom_validation_score:
      type: int
      custom_validation:
        - condition: custom_validation_score >= 0 and custom_validation_score <= 100
          error_message: "Score must be between 0 and 100."
  vars:
    custom_validation_score: 85

```

But what if we have a list of users with score

```yaml
users:
   - name: alice
     score: 50
   - name: bob
     score: 200

```

How validate that for all users score is within 0 and 100?

```yaml
- capable.core212.validate_vars:
    users:
      type: list
      elements:
          type: dict
          options:
              name: 
                 type: str
              score:
                 type: int
                 custom_validation:
                    - condition: this >= 0 and this <= 100
                      error_message: "Score must be between 0 and 100 for all users"
  vars:
    users:
      - name: alice
        score: 50
      - name: bob
        score: 200

```

Here we validate that users is a list, each element of this list is a dict, and dict has at least `name` and `score` attributes, and `score` for each user is within 0 and 100.  
Pay special attention to use of `this` keyword (only available for this plugin, not generic ansible feature). Using `this` allow to have validations for nested data (in this case or scores of each users)

There are more features and possible validatation patterns for this plugin. I will followup with them in this topic. So it is not overwhelming to see everything all at once.

PS here is a proper link to documentation  
[https://capable-core.github.io/collections/capable/core212/modules/validate\_vars/](https://capable-core.github.io/collections/capable/core212/modules/validate_vars/)