place_stop_order

THE RISK

Critical Risk

Why place_stop_order needs a policy

Despite the empty description, the tool name 'place_stop_order' clearly indicates it places a stop order on a financial trading platform. Given the server's explicit purpose of trading via Alpaca API and the sibling tools all being order/trade related, this tool commits financial obligations by placing a stop order in the market.

From the tool's definition Tool name 'place_stop_order' on a server described as interfacing with Alpaca trading API to 'place trades'; sibling tools include 'place_market_order', 'place_limit_order', 'place_stop_limit_order' confirming this is an order placement tool.

Documented attack patterns abuse exactly the kind of access place_stop_order gives an agent:

POLICY

How to control place_stop_order

PolicyLayer is an MCP gateway — it sits between your AI agents and Alpaca Trading MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for place_stop_order:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "place_stop_order": {
      "deny_if": [
        {
          "conditions": [],
          "on_deny": "Requires human approval."
        }
      ]
    }
  }
}

Any call to place_stop_order is blocked until a human approves it. The rest of the server keeps working.

Create a free account and register Alpaca Trading MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

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EXPLORE

Related tools and policies

More Alpaca Trading MCP Server tools

Financial place_stop_limit_order place_stop_limit_order Financial place_limit_order place_limit_order Financial place_market_order Place a market order to buy or sell a stock. Financial close_position Close an open position for a specific symbol. Destructive cancel_order Cancel an open order by its ID. Read get_account_info_tool Get current account information. Read get_portfolio_summary Get a comprehensive summary of the portfolio including account details and open positions.

All 8 Alpaca Trading MCP Server tools →

Financial tools on other servers

0xarchive web3_subscribe Math MCP Server financial_calculator MCP Kling generate_video MCP Uber Server uber_request_ride

Go deeper

Critical-risk tools in Alpaca Trading MCP Server → Every critical-risk tool this server exposes, in one view.
All critical-risk MCP tools → Every critical-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Human-in-the-loop → When a tool call should wait for a person — and when policy can decide alone.
Tool call approval → Approval gates on individual tool calls: auto-allow, prompt, or deny.
How to Add Spending Controls to Any MCP Agent →
Rate Limiting MCP Tool Calls: A Practical Guide →

FAQ

Questions about place_stop_order

What does the place_stop_order tool do? +

place_stop_order. It is categorised as a Financial tool in the Alpaca Trading MCP Server MCP Server, which means it involves financial transactions. Block by default and require explicit approval.

How do I enforce a policy on place_stop_order? +

Register the Alpaca Trading MCP Server MCP server in PolicyLayer and add a rule for place_stop_order: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Alpaca Trading MCP Server. Nothing to install.

What risk level is place_stop_order? +

place_stop_order is a Financial tool with critical risk. Critical-risk tools should be blocked by default and only enabled with explicit human approval.

Can I rate-limit place_stop_order? +

Yes. Add a rate_limit block to the place_stop_order rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block place_stop_order completely? +

Set action: deny in the PolicyLayer policy for place_stop_order. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides place_stop_order? +

place_stop_order is provided by the Alpaca Trading MCP Server MCP server (laukikk/alpaca-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Alpaca Trading MCP Server tool call.

Start from Alpaca Trading MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →