Get the purchase or delivery link for a product. Free items return the delivery URL directly. Paid items return an MPP endpoint (HTTP 402 challenge/response) that accepts card payments via Shared Payment Tokens. Use search-underground first to find product IDs.
AI agents use buy-from-underground to commit financial operations through Underground Cultural District MCP Server — usually the final step of a payment, billing, or trading workflow. A call moves real money.
This tool initiates or completes financial transactions by processing card payments through Stripe checkout for paid digital products. It directly involves committing financial obligations (charging a payment method), making it Financial category. The critical severity reflects that an AI agent misusing this tool could make unauthorized purchases on behalf of users.
From the tool's definition "buy-from-underground", "accepts card payments via Shared Payment Tokens", "Paid items return an MPP endpoint (HTTP 402 challenge/response) that accepts card payments"
Attacks that exploit this kind of access
Get the purchase or delivery link for a product. Free items return the delivery URL directly. Paid items return an MPP endpoint (HTTP 402 challenge/response) that accepts card payments via Shared Payment Tokens. Use search-underground first to find product IDs. It is categorised as a Financial tool in the Underground Cultural District MCP Server MCP Server, which means it involves financial transactions. Block by default and require explicit approval.
Register the Underground Cultural District MCP Server MCP server in PolicyLayer and add a rule for buy-from-underground: 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 Underground Cultural District MCP Server. Nothing to install.
buy-from-underground is a Financial tool with critical risk. Critical-risk tools should be blocked by default and only enabled with explicit human approval.
Yes. Add a rate_limit block to the buy-from-underground 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.
Set action: deny in the PolicyLayer policy for buy-from-underground. 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.
buy-from-underground is provided by the Underground Cultural District MCP Server MCP server (lisamaraventano-spine/mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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