update_cart · Mcp Costco MCP: Risk & Policy

WHAT IT DOES

What update_cart does on Mcp Costco

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

WHY IT NEEDS A POLICY

Why update_cart needs a policy

This tool modifies cart state by updating quantities or removing items. These are reversible operations—items can be re-added and quantities adjusted again. The blast radius is confined to the current shopping session/cart. It does not execute financial transactions (checkout is a separate tool), delete permanent data, or execute arbitrary code.

From the tool's definition Tool performs reversible modifications: 'Update item quantities or remove items from the Costco cart'. While described as 'remove', the context indicates this is cart management (reversible state change), not destructive deletion of permanent data.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_cart Rate-limited

update_cart 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_cart": {
      "limits": [
        {
          "counter": "update_cart_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 Mcp Costco, so you can run agents against it safely.

FAQ

Questions about update_cart

What does the update_cart tool do? +

Update item quantities or remove items from the Costco cart. It is categorised as a Write tool in the Mcp Costco 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_cart? +

Register the Mcp Costco MCP server in PolicyLayer and add a rule for update_cart: 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 Mcp Costco. Nothing to install.

What risk level is update_cart? +

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

Can I rate-limit update_cart? +

Yes. Add a rate_limit block to the update_cart 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_cart completely? +

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

update_cart is provided by the Mcp Costco MCP server (markswendsen-code/mcp-costco). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.