> ## Documentation Index
> Fetch the complete documentation index at: https://docs.agno.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Output Guardrail

> Reject responses under 20 characters with a post-hook that raises OutputCheckError.

```python output_guardrail.py theme={null}
"""
Output Guardrail
=============================

Output Guardrail.
"""

from agno.agent import Agent
from agno.exceptions import CheckTrigger, OutputCheckError
from agno.models.openai import OpenAIResponses
from agno.run.agent import RunOutput


def enforce_non_empty_output(run_output: RunOutput) -> None:
    """Reject empty or very short responses."""
    content = (run_output.content or "").strip()
    if len(content) < 20:
        raise OutputCheckError(
            "Output is too short to be useful.",
            check_trigger=CheckTrigger.OUTPUT_NOT_ALLOWED,
        )


# ---------------------------------------------------------------------------
# Create Agent
# ---------------------------------------------------------------------------
agent = Agent(
    name="Output-Checked Agent",
    model=OpenAIResponses(id="gpt-5.2"),
    post_hooks=[enforce_non_empty_output],
)

# ---------------------------------------------------------------------------
# Run Agent
# ---------------------------------------------------------------------------
if __name__ == "__main__":
    agent.print_response("Summarize the key ideas in clean architecture.", stream=True)
```

## Run the Example

<Steps>
  <Snippet file="create-venv-step.mdx" />

  <Step title="Install dependencies">
    ```bash theme={null}
    uv pip install -U agno openai
    ```
  </Step>

  <Step title="Export your OpenAI API key">
    <CodeGroup>
      ```bash Mac/Linux theme={null}
      export OPENAI_API_KEY="your_openai_api_key_here"
      ```

      ```bash Windows theme={null}
      $Env:OPENAI_API_KEY="your_openai_api_key_here"
      ```
    </CodeGroup>
  </Step>

  <Step title="Run the example">
    Save the code above as `output_guardrail.py`, then run:

    ```bash theme={null}
    python output_guardrail.py
    ```
  </Step>
</Steps>

Full source: [cookbook/02\_agents/08\_guardrails/output\_guardrail.py](https://github.com/agno-agi/agno/blob/main/cookbook/02_agents/08_guardrails/output_guardrail.py)