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

# API Authentication

> How to authenticate requests to the LLM Gateway API

The Better Data LLM Gateway API uses standard HTTP headers to verify the identity and permissions of its clients.

## API Keys

For server-to-server communication or when using a self-hosted gateway with a predefined key list.

**Header:**

```
Authorization: Bearer YOUR_API_KEY
```

You can configure these keys in your `LLMGateway` [Configuration](/reference/configuration).

## Session IDs

To maintain state in a conversational context, include a `X-Session-Id` header. This allows the gateway to link the request to a specific user's cart and history.

**Header:**

```
X-Session-Id: unique_session_string_123
```

## Better Data Cloud Keys

If you are using the [Hosted Gateway](/hosted/overview), you must use your Cloud API keys generated in the dashboard. These keys are scoped to your specific account and entitlements.

## Secure Link Authentication

When transferring a session from an AI (like Claude) to a web storefront, the gateway generates a short-lived, single-use **Secure Link Token**. This token is passed as a query parameter and automatically upgraded to a full session cookie by the storefront.

**Example Link:**

```
https://mystore.com/checkout?token=st_abc123
```

## Best Practices

* **Never Expose Secret Keys**: Use Public Keys for frontend tool discovery and Secret Keys only for backend tool execution.
* **Environment Variables**: Always store your keys in secure environment variables, never hardcode them in your source.
* **HTTPS Only**: All API requests must be made over TLS 1.2 or higher.