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

# MessagesRequestMetadata

## Fields

| Field    | Type                                         | Required             | Description |
| -------- | -------------------------------------------- | -------------------- | ----------- |
| `UserID` | optionalnullable.OptionalNullable\[`string`] | :heavy\_minus\_sign: | N/A         |