add_to_cart · FakeStore MCP: Risk & Policy

WHAT IT DOES

What add_to_cart does on FakeStore MCP

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

WHY IT NEEDS A POLICY

Why add_to_cart needs a policy

Adding items to a cart modifies user state (the cart contents) but is reversible—items can be removed via remove_from_cart or the cart can be cleared via clear_cart. This is a classic Write operation: it creates or modifies data without permanent deletion.

From the tool's definition Tool name 'add_to_cart' and description 'Add item to user' indicate creation/modification of shopping cart state. This is a write operation that creates or modifies cart data reversibly.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

add_to_cart Rate-limited

add_to_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": {
    "add_to_cart": {
      "limits": [
        {
          "counter": "add_to_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 FakeStore MCP, so you can run agents against it safely.

FAQ

Questions about add_to_cart

What does the add_to_cart tool do? +

Add item to user. It is categorised as a Write tool in the FakeStore MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on add_to_cart? +

Register the FakeStore MCP server in PolicyLayer and add a rule for add_to_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 FakeStore MCP. Nothing to install.

What risk level is add_to_cart? +

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

Can I rate-limit add_to_cart? +

Yes. Add a rate_limit block to the add_to_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 add_to_cart completely? +

Set action: deny in the PolicyLayer policy for add_to_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 add_to_cart? +

add_to_cart is provided by the FakeStore MCP server (mithgroth/fakestore-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.