> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs.auxiliar.ai/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.auxiliar.ai/_mcp/server.

# Authentication

Auxiliar authenticates with a single **API key**, sent as a bearer token. The same key works across every tool — there's no need to sign up for, or manage a separate key for, each individual service. You never send a provider's own key; Auxiliar adds it for you.

Include your key on every request:

```
Authorization: Bearer YOUR_API_KEY
```

## Example

```bash
curl -X POST "https://api.auxiliar.ai/serper" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"q": "apple inc"}'
```

A request with a missing or invalid key returns **`401 Unauthorized`**.

Treat your API key like a password — anyone with it can make requests on your account. Keep it in an environment variable or secret manager, and never expose it in client-side code or commit it to version control.