> Fetch clean Markdown by appending `.md` to any page URL under https://signalwire.com/docs or requesting it with the HTTP header `Accept: text/markdown`. The root index at https://signalwire.com/docs/llms.txt lists the available documentation indexes.

# prepare

> Validate a browser request and build the upstream JSON-RPC call, without FastAPI.

[ref-chatgateway]: /docs/server-sdks/reference/python/agents/chat-gateway

[router]: /docs/server-sdks/reference/python/agents/chat-gateway/router

[aichatclient]: /docs/server-sdks/reference/python/agents/ai-chat-client

Validate a browser request and build the upstream call. This is the framework-agnostic core of the
gateway, for serving it from something other than FastAPI. With FastAPI, use [`router()`][router]
instead.

Everything the browser could use to widen its own access is either rejected or overwritten here: the
method must be one of the four, the conversation comes from a signed handle, and `config_url` is the
gateway's.

## **Parameters**

**`body`** `dict[str, Any]` — required

The parsed request body, carrying `method` and, depending on the method, `handle` and `message`.

---

**`origin`** `str | None` — required

The request's `Origin` header. Keyword-only. `None` is allowed, since a non-browser caller sends
none and refusing those would break server-side use without stopping an attacker, who simply omits
the header.

---

**`key`** `str | None` — required

The publishable key from `Authorization: Bearer`. Keyword-only.

---

## **Returns**

`tuple[str, dict[str, Any], str | None]` — the upstream method name, its params, and a newly minted
handle. The handle is set only on the call that created the conversation, so you can hand it back in
the `X-Chat-Handle` header.

The upstream method is the service's, not the browser's: `start` becomes `create_conversation`, `end`
becomes `end_conversation`, and `log` becomes `chat_log`.

## **Raises**

`GatewayRejection` for a bad key (`401`), a disallowed origin (`403`), a bad or expired handle
(`403`), an unknown method or missing message (`400`), or a cap hit (`429`).

## **Example**

Serving the gateway from a framework of your own, forwarding with
[`AIChatClient`][aichatclient]:

```python {9,13}
from signalwire.ai_chat import AIChatClient, ChatGateway, GatewayRejection

client = AIChatClient(space="your-space")
gateway = ChatGateway(config_url="https://bayview-taxi.example.com/swml", client=client)


async def handle_request(body, origin, key):
    try:
        method, params, minted = gateway.prepare(body, origin=origin, key=key)
    except GatewayRejection as rejection:
        return rejection.status, {"error": rejection.reason}, None

    async with client.raw_post(method, params) as resp:
        payload = await resp.read()

    return 200, payload, minted
```

> Validate a browser request and build the upstream JSON-RPC call, without FastAPI.