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

# Authentication

> Authenticate server-side requests with a bearer API key.

Send your YingTu API key in the `Authorization` header on every request.

```http theme={null}
Authorization: Bearer $YINGTU_API_KEY
```

<Warning>Never expose an API key in client-side code or public logs.</Warning>

Use separate keys per environment and rotate any key that may have been
disclosed.