> ## Documentation Index
> Fetch the complete documentation index at: https://agno-v2-docs-scavio-google-v2.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# BaseGuardrail

> Abstract base class for custom guardrails. Implement check and async_check to validate run input.

`BaseGuardrail` is the abstract base class for guardrails. Subclass it and implement `check` and `async_check` to build a custom guardrail.

```python theme={null}
from agno.guardrails import BaseGuardrail
```

## Methods

### `check`

Perform the guardrail checks synchronously.

**Parameters:**

* `run_input` (RunInput | TeamRunInput): The input provided to the Agent or Team when invoking the run.

**Returns:** `None`

### `async_check`

Perform the guardrail checks asynchronously.

**Parameters:**

* `run_input` (RunInput | TeamRunInput): The input provided to the Agent or Team when invoking the run.

**Returns:** `None`