> ## 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 Trace Start • AI Agent SDK

> on_trace_start: Called when a trace starts.

# on\_trace\_start

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

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

Called when a trace starts.

## Signature

```python theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
def on_trace_start(trace_id: str, session_id: Optional[str], agent_name: Optional[str], user_id: Optional[str], metadata: Optional[Dict[str, Any]]) -> None
```

## Parameters

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

<ParamField query="session_id" type="Optional" required={false}>
  No description available.
</ParamField>

<ParamField query="agent_name" type="Optional" required={false}>
  No description available.
</ParamField>

<ParamField query="user_id" type="Optional" required={false}>
  No description available.
</ParamField>

<ParamField query="metadata" type="Optional" required={false}>
  No description available.
</ParamField>

## Source

<Card title="View on GitHub" icon="github" href="https://github.com/MervinPraison/PraisonAI/blob/main/src/praisonai-agents/praisonaiagents/obs/__init__.py#L60">
  `praisonaiagents/obs/__init__.py` at line 60
</Card>