> ## 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.

# On Message • AI Agent SDK

> on_message: Register a message handler.

# on\_message

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

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

Register a message handler.

## Signature

```python theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
def on_message(handler: Callable[[BotMessage], Any]) -> Callable
```

## Parameters

<ParamField query="handler" type="Callable" required={true}>
  Function to call when a message is received
</ParamField>

### Returns

<ResponseField name="Returns" type="Callable">
  The handler function (for decorator use)
</ResponseField>

## Source

<Card title="View on GitHub" icon="github" href="https://github.com/MervinPraison/PraisonAI/blob/main/src/praisonai-agents/praisonaiagents/bots/protocols.py#L399">
  `praisonaiagents/bots/protocols.py` at line 399
</Card>