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

# OnTokenCallback

```ts theme={null}
type OnTokenCallback = (token) => void;
```

Defined in: [client/sampling/types.ts:13](https://github.com/PrefectHQ/fastmcp-ts/blob/e4b6038f642b529f601463a576229747afebe9a4/src/client/sampling/types.ts#L13)

Called with each text token as it is streamed from the provider.

## Parameters

### token

`string`

## Returns

`void`