Look up a MERX invoice. Shows amount, recipient, token, and status. Agent must sign and broadcast the transfer separately (non-custodial).
AI agents call lookup_invoice to retrieve information from MERX - TRON Resource Exchange without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves and displays invoice information without modifying data or executing transactions. The non-custodial design ensures the tool itself cannot move funds or commit financial obligations; that requires separate agent action. Therefore, it is classified as Read with low severity, as misuse would only expose invoice data, not enable unauthorized transfers.
From the tool's definition Tool description states 'Look up a MERX invoice. Shows amount, recipient, token, and status.' The verb 'look up' and 'shows' indicate data retrieval with no side effects.
Attacks that exploit this kind of access
Look up a MERX invoice. Shows amount, recipient, token, and status. Agent must sign and broadcast the transfer separately (non-custodial). It is categorised as a Read tool in the MERX - TRON Resource Exchange MCP Server, which means it retrieves data without modifying state.
Register the MERX - TRON Resource Exchange MCP server in PolicyLayer and add a rule for lookup_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.
lookup_invoice is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the lookup_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 lookup_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.
lookup_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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