Equity legs in multi-leg orders

Alpaca Integration Applications
1

Hi there, I am trying to set up a multileg order submission function. So far I have no problem creating a multileg option order. However, if I want to include stock into the leg to create, for example, a covered call structure, then it always throw the following error:
equity legs are allowed only with a corresponding amount of call contracts. This error persists no matter what I change about the method (changing ratio quantity, closing an existing position instead of opening, etc.)

Any insights on how to set it up?

import requests
def option_test():
    short_symbol='SPY260821C00743000'
    stock_symbol='SPY'
    quantity=1
    limit_price=720

    global api_key,secret_key
    
    if not api_key or not secret_key:
        raise ValueError("API keys missing!")

    url = "https://paper-api.alpaca.markets/v2/orders"
    
    headers = {
        "accept": "application/json",
        "content-type": "application/json",
        "APCA-API-KEY-ID": api_key,
        "APCA-API-SECRET-KEY": secret_key
    }
    
    payload = {
        "order_class": "mleg",
        "type": "limit",
        "limit_price": str(limit_price),
        "time_in_force": "day",
        "qty": str(quantity),
        "legs": [
            {
                "symbol": short_symbol,
                "side": "sell",
                "ratio_qty": "1",
                "position_intent": "sell_to_open"
            },
            {
                "symbol": stock_symbol,
                "side": "buy",
                "ratio_qty": "1",
                "position_intent": "buy_to_open"
            }
        ]
    }
    
    try:
        response = requests.post(url, json=payload, headers=headers)
        response.raise_for_status() 
        order_data = response.json()
        print(f"Successfully submitted live close order via REST API. Order ID: {order_data.get('id')}")
        return order_data
    except requests.exceptions.HTTPError as http_err:
        try:
            error_msg = response.json()
        except Exception:
            error_msg = response.text
        print(f"Alpaca API Error: {error_msg}")
        raise http_err
    except Exception as e:
        print(f"Failed to submit live order: {e}")
        raise e