marketplace_purchase

THE RISK

Critical Risk

Why marketplace_purchase needs a policy

The name 'marketplace_purchase' indicates this tool completes a purchase/buy action on a marketplace, which constitutes a financial commitment. Despite the empty description, the sibling tools (marketplace_publish, marketplace_my_listings, marketplace_my_metrics) confirm this is a real marketplace with listings and transactions.

From the tool's definition Tool name 'marketplace_purchase' strongly implies a financial transaction (purchasing items from a marketplace).

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

POLICY

How to control marketplace_purchase

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

policy.json

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

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

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

GATE THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Loreto tools

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All 13 Loreto tools →

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Go deeper

Critical-risk tools in Loreto → 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 marketplace_purchase

What does the marketplace_purchase tool do? +

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

How do I enforce a policy on marketplace_purchase? +

Register the Loreto MCP server in PolicyLayer and add a rule for marketplace_purchase: 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 Loreto. Nothing to install.

What risk level is marketplace_purchase? +

marketplace_purchase 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 marketplace_purchase? +

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

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

marketplace_purchase is provided by the Loreto MCP server (kopias/loreto-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Loreto tool call.

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

CHECK YOUR STACK →