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

# MCP authentication & scoping

> How the Brew MCP server authenticates — a native OAuth connector or a brand-scoped API key — scopes every call to one brand, and makes writes safe to retry.

## Authentication

The connection URL is clean and the same for everyone:

```
https://brew.new/api/mcp
```

There are two ways to authenticate it.

<AccordionGroup>
  <Accordion title="OAuth connector (recommended)" defaultOpen>
    Brew is its own **OAuth 2.1 authorization server**, so most clients connect with **no key to copy**. Add the URL as a connector; on first connect the client opens your browser to **sign in with Brew** and **pick a brand**. Brew issues a token scoped to that brand — you can see and revoke it under **Settings → API** ("Connected via OAuth"). This is the first-party flow for Claude, ChatGPT, Cursor, VS Code, and the rest — see [Connect your client](/api-reference/mcp/connect-your-client).
  </Accordion>

  <Accordion title="API key (alternative)">
    For clients with no OAuth UI, or headless / CI setups, send a **brand-scoped API key** as a bearer token instead:

    ```
    Authorization: Bearer brew_YOUR_API_KEY
    ```

    Create keys at **Settings → API**. A request with no / invalid credential returns `401`.
  </Accordion>
</AccordionGroup>

## Brand scoping

Every connection is **scoped to exactly one brand** — and there is no brand in the URL. With OAuth you choose the brand when you sign in; with an API key the key itself carries the org + brand. Either way the token or key determines the brand for every call. To operate on a different brand, connect again and pick it (OAuth) or use that brand's key. Find brand details via the `get_brand` tool or the dashboard.

## Safe retries (idempotency)

Every **write** tool accepts an optional `idempotency_key` (≤ 100 chars). A repeat call with the **same key** replays the original result instead of acting twice; the same key with a **different payload** returns `409 IDEMPOTENCY_CONFLICT`. This reuses the API's Redis reserve/replay, so a key is honored identically across the MCP and HTTP surfaces. Always pass one on `send_email` — it is fail-closed (refuses with a retryable `503` if dedupe can't be guaranteed) so a retry never sends a campaign twice.

## Errors & observability

Errors surface with an actionable `code`, `message`, `suggestion`, and a `request_id` you can quote to support. Out-of-credits → `INSUFFICIENT_CREDITS`. Permission gaps and validation failures each return a distinct code.

## Need Help?

Our team is ready to support you at every step of your journey with Brew. Choose the option that works best for you:

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