update_watchlist · Alpaca MCP Server MCP: Risk & Policy

WHAT IT DOES

What update_watchlist does on Alpaca MCP Server

AI agents use update_watchlist to create or update resources in Alpaca MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Alpaca MCP Server environment.

WHY IT NEEDS A POLICY

Why update_watchlist needs a policy

This tool creates or modifies data (watchlist contents) in a reversible manner. It does not delete data (would be Destructive), execute arbitrary code (would be Execute), move money (would be Financial), or merely read data (would be Read). The severity is medium because misuse could affect investment decision-making by poisoning watchlist data, but the impact is limited to one user's watchlist and is reversible.

From the tool's definition Tool name is 'update_watchlist' and description states 'Update an existing watchlist.' The verb 'update' indicates modification of existing data (a watchlist), which is a reversible write operation.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_watchlist Rate-limited

update_watchlist stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "update_watchlist": {
      "limits": [
        {
          "counter": "update_watchlist_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Alpaca MCP Server, so you can run agents against it safely.

FAQ

Questions about update_watchlist

What does the update_watchlist tool do? +

Update an existing watchlist. It is categorised as a Write tool in the Alpaca MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on update_watchlist? +

Register the Alpaca MCP Server MCP server in PolicyLayer and add a rule for update_watchlist: 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 MCP Server. Nothing to install.

What risk level is update_watchlist? +

update_watchlist is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit update_watchlist? +

Yes. Add a rate_limit block to the update_watchlist 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 update_watchlist completely? +

Set action: deny in the PolicyLayer policy for update_watchlist. 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 update_watchlist? +

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