# UsageMetadata

> **Type Alias** in `@langchain/core`

📖 [View in docs](https://reference.langchain.com/javascript/langchain-core/messages/UsageMetadata)

Usage metadata for a message, such as token counts.

## Signature

```javascript
UsageMetadata
```

## Properties

- `input_token_details`
- `input_tokens`
- `output_token_details`
- `output_tokens`
- `total_tokens`

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[View source on GitHub](https://github.com/langchain-ai/langchainjs/blob/2a5713dfbc5987fb1dcf85cd1de9379816688927/libs/langchain-core/src/messages/metadata.ts#L140)