Pay an x402 invoice by signing and broadcasting a TRX transfer to the invoice address, then verifying the payment with the facilitator. x402 (Coinbase + Cloudflare HTTP 402 standard) is the protocol AI agents use to pay APIs per call. Use this when you receive an invoice_id from a paywalled servi...
AI agents use pay_invoice to commit financial operations through MERX - TRON Resource Exchange — usually the final step of a payment, billing, or trading workflow. A call moves real money.
This tool moves money (TRX cryptocurrency) on the TRON blockchain to pay invoices. It requires private key management and broadcasts actual financial transactions. This is unambiguously a Financial category tool.
From the tool's definition Tool description explicitly states it 'Pay[s] an x402 invoice by signing and broadcasting a TRX transfer' and requires 'TRON_PRIVATE_KEY'.
Attacks that exploit this kind of access
Pay an x402 invoice by signing and broadcasting a TRX transfer to the invoice address, then verifying the payment with the facilitator. x402 (Coinbase + Cloudflare HTTP 402 standard) is the protocol AI agents use to pay APIs per call. Use this when you receive an invoice_id from a paywalled service or another agent. REQUIRES: TRON_PRIVATE_KEY in env (use set_private_key first) AND a valid invoice_id from create_invoice or x402 challenge response. The transfer is signed locally — your private key never leaves the MCP process. It is categorised as a Financial tool in the MERX - TRON Resource Exchange MCP Server, which means it involves financial transactions. Block by default and require explicit approval.
Register the MERX - TRON Resource Exchange MCP server in PolicyLayer and add a rule for pay_invoice: 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 MERX - TRON Resource Exchange. Nothing to install.
pay_invoice 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 pay_invoice 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 pay_invoice. 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.
pay_invoice is provided by the MERX - TRON Resource Exchange MCP server (Hovsteder/merx-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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