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

# Add Definition • Rust AI Agent SDK

> add_definition: Add a hook definition

# add\_definition

<div className="flex items-center gap-2">
  <Badge color="purple">Method</Badge>
</div>

> This is a method of the [**HookRegistry**](../classes/HookRegistry) class in the [**hooks**](../modules/hooks) module.

Add a hook definition

## Signature

```python theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
def add_definition(&mut self, hook: HookDefinition) -> &mut Self
```

## Parameters

<ParamField query="hook" type="HookDefinition" required={true}>
  No description available.
</ParamField>

### Returns

<ResponseField name="Returns" type="&mut Self">
  The result of the operation.
</ResponseField>