# ToolOutputMixin

> **Class** in `langchain_core`

📖 [View in docs](https://reference.langchain.com/python/langchain-core/messages/tool/ToolOutputMixin)

Mixin for objects that tools can return directly.

If a custom BaseTool is invoked with a `ToolCall` and the output of custom code is
not an instance of `ToolOutputMixin`, the output will automatically be coerced to
a string and wrapped in a `ToolMessage`.

## Signature

```python
ToolOutputMixin()
```

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[View source on GitHub](https://github.com/langchain-ai/langchain/blob/1c3a4186cf2ba4f28face59118ac7786de009f91/libs/core/langchain_core/messages/tool.py#L16)