Alpaca Trading MCP Server

Instructions

Implementation Reference

• src/server.py:377-437 (handler)

  The primary handler function for the 'place_stop_order' MCP tool. It handles input validation using enums, constructs an AlpacaOrderRequest with STOP order type, delegates to calls.place_order for execution, and formats the response.

  @mcp.tool()
  def place_stop_order(
      symbol: str, 
      quantity: float, 
      side: str, 
      stop_price: float,
      time_in_force: str = "day"
  ) -> str:
      """
      Place a stop order to buy or sell a stock when it reaches a specified price.
      
      Args:
          symbol: Stock symbol (e.g., 'AAPL')
          quantity: Number of shares to buy or sell (can be fractional)
          side: Either 'buy' or 'sell'
          stop_price: Price that triggers the order
          time_in_force: Order duration - 'day', 'gtc' (good till canceled)
      
      Returns:
          Order confirmation details
      """
      # Validate side
      try:
          order_side = AlpacaOrderSide(side.lower())
      except ValueError:
          return f"Invalid side: {side}. Must be 'buy' or 'sell'."
      
      # Validate time in force
      try:
          order_tif = AlpacaTimeInForce(time_in_force.lower())
      except ValueError:
          return f"Invalid time in force: {time_in_force}. Valid options are: day, gtc"
      
      # Create order request
      order_request = AlpacaOrderRequest(
          symbol=symbol,
          qty=float(quantity),
          side=order_side,
          type=AlpacaOrderType.STOP,
          time_in_force=order_tif,
          stop_price=float(stop_price)
      )
      
      try:
          order = calls.place_order(trading_client, order_request)
          
          return (
              f"Stop order placed successfully!\n\n"
              f"Order ID: {order.id}\n"
              f"Symbol: {order.symbol}\n"
              f"Side: {order.side.value}\n"
              f"Type: {order.type.value}\n"
              f"Quantity: {order.qty}\n"
              f"Stop Price: ${order.stop_price:.2f}\n"
              f"Time in Force: {order.time_in_force.value}\n"
              f"Status: {order.status.value}\n"
              f"Created At: {order.created_at}\n"
          )
      except Exception as e:
          return f"Error placing stop order: {str(e)}"

• src/models.py:87-97 (schema)

  Pydantic model defining the structure and validation for order requests, including the stop_price field used by stop orders. Provides type safety and validation for the tool's inputs.

  class AlpacaOrderRequest(BaseModel):
      symbol: str
      qty: Union[int, float]
      side: AlpacaOrderSide
      type: AlpacaOrderType
      time_in_force: AlpacaTimeInForce
      limit_price: Optional[float] = None
      stop_price: Optional[float] = None
      client_order_id: Optional[str] = None
      extended_hours: Optional[bool] = False

• src/calls.py:44-96 (helper)

  Helper function that translates the generic AlpacaOrderRequest into Alpaca-specific StopOrderRequest for STOP orders and submits it to the trading client via submit_order.

  def place_order(client: TradingClient, order_details: AlpacaOrderRequest):
      """
      Place an order with flexible order types
      
      :param client: Alpaca trading client
      :param order_details: Order request details
      :return: Placed AlpacaOrder
      """
      # Map Pydantic model to Alpaca order request based on order type
      if order_details.type == AlpacaOrderType.MARKET:
          order_request = MarketOrderRequest(
              symbol=order_details.symbol,
              qty=order_details.qty,
              side=order_details.side,
              time_in_force=order_details.time_in_force
          )
      elif order_details.type == AlpacaOrderType.LIMIT:
          if not order_details.limit_price:
              raise ValueError("Limit price is required for limit orders")
          order_request = LimitOrderRequest(
              symbol=order_details.symbol,
              qty=order_details.qty,
              side=order_details.side,
              time_in_force=order_details.time_in_force,
              limit_price=order_details.limit_price
          )
      elif order_details.type == AlpacaOrderType.STOP:
          if not order_details.stop_price:
              raise ValueError("Stop price is required for stop orders")
          order_request = StopOrderRequest(
              symbol=order_details.symbol,
              qty=order_details.qty,
              side=order_details.side,
              time_in_force=order_details.time_in_force,
              stop_price=order_details.stop_price
          )
      elif order_details.type == AlpacaOrderType.STOP_LIMIT:
          if not (order_details.stop_price and order_details.limit_price):
              raise ValueError("Both stop and limit prices are required for stop-limit orders")
          order_request = StopLimitOrderRequest(
              symbol=order_details.symbol,
              qty=order_details.qty,
              side=order_details.side,
              time_in_force=order_details.time_in_force,
              stop_price=order_details.stop_price,
              limit_price=order_details.limit_price
          )
      else:
          raise ValueError(f"Unsupported order type: {order_details.type}")
  
      # Submit order
      order = client.submit_order(order_request)
      return AlpacaOrder(**order.__dict__)

• src/models.py:25-31 (schema)

  Enum defining order types, including STOP used in the tool.

  class AlpacaOrderType(str, Enum):
      MARKET = 'market'
      LIMIT = 'limit'
      STOP = 'stop'
      STOP_LIMIT = 'stop_limit'
      TRAILING_STOP = 'trailing_stop'

• src/server.py:377-377 (registration)

  The @mcp.tool() decorator registers the place_stop_order function as an MCP tool.

  @mcp.tool()