> ## Documentation Index
> Fetch the complete documentation index at: https://docs.021labs.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# instrument_baml()

> Wrap a BAML client with automatic tracing

## Signature

```python theme={null}
def instrument_baml(baml_client: Any) -> Any
```

## Overview

Unlike Anthropic, OpenAI, LangChain, and Gemini — which are auto-instrumented automatically — BAML clients are code-generated per project and cannot be monkey-patched. You must explicitly wrap the client with `instrument_baml()`.

<Warning>
  If you use BAML without calling `instrument_baml()`, calls will **not** be traced. There is no error — they simply won't appear in traces.
</Warning>

## Parameters

<ParamField path="baml_client" type="Any" required>
  The BAML client instance to wrap. Typically imported as `b` from `baml_client`.
</ParamField>

## Returns

A proxy-wrapped client with tracing enabled. Assign the result back to your client variable.

## Example

```python theme={null}
from baml_client import b
from rdk import observe, instrument_baml

# Required: wrap the BAML client before use
b = instrument_baml(b)

@observe(name="extract-entities")
async def process(text: str):
    return await b.ExtractEntities(text)  # Auto-traced!
```

## How It Works

`instrument_baml()` wraps the BAML client in a proxy that intercepts method calls. When a BAML function is called:

1. The proxy detects the active trace (from `@observe` or `trace()`)
2. A span is created with the function name and arguments
3. The real BAML function executes normally
4. The span is completed with the structured result and token usage

## What Gets Captured

| Field               | Description                                       |
| ------------------- | ------------------------------------------------- |
| `type`              | `LLM`                                             |
| `name`              | BAML function name (e.g., `baml.ClassifyInquiry`) |
| `input.args`        | Function arguments                                |
| `output.result`     | Structured result                                 |
| `token_usage`       | Token counts                                      |
| `metadata.provider` | `"baml"`                                          |

## See Also

* [BAML Integration](/integrations/baml) — Full setup guide
* [@observe](/api-reference/observe) — Create a trace context