x402_payment_signature_exact_scheme_create

THE RISK

Critical Risk

Why x402_payment_signature_exact_scheme_create needs a policy

This tool creates payment signatures for cryptocurrency transactions on a server explicitly designed to 'send Nano cryptocurrency.' A payment signature is the authorization step that enables financial transfers; misuse could authorize unintended crypto payments. The context of sibling tools like 'nano_send' and 'raw_send' confirms this is part of a financial transaction workflow.

From the tool's definition 'Create the PAYMENT-SIGNATURE header for Nano exact scheme x402 transaction' — creates cryptographic payment authorization for Nano cryptocurrency transactions

Documented attack patterns abuse exactly the kind of access x402_payment_signature_exact_scheme_create gives an agent:

POLICY

How to control x402_payment_signature_exact_scheme_create

PolicyLayer is an MCP gateway — it sits between your AI agents and Nano Currency MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for x402_payment_signature_exact_scheme_create:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "x402_payment_signature_exact_scheme_create": {
      "deny_if": [
        {
          "conditions": [],
          "on_deny": "Requires human approval."
        }
      ]
    }
  }
}

Any call to x402_payment_signature_exact_scheme_create is blocked until a human approves it. The rest of the server keeps working.

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

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EXPLORE

Related tools and policies

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Go deeper

Critical-risk tools in Nano Currency MCP Server → 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 x402_payment_signature_exact_scheme_create

What does the x402_payment_signature_exact_scheme_create tool do? +

Create the PAYMENT-SIGNATURE header for Nano exact scheme x402 transaction. It is categorised as a Financial tool in the Nano Currency MCP Server MCP Server, which means it involves financial transactions. Block by default and require explicit approval.

How do I enforce a policy on x402_payment_signature_exact_scheme_create? +

Register the Nano Currency MCP Server MCP server in PolicyLayer and add a rule for x402_payment_signature_exact_scheme_create: 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 Nano Currency MCP Server. Nothing to install.

What risk level is x402_payment_signature_exact_scheme_create? +

x402_payment_signature_exact_scheme_create 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 x402_payment_signature_exact_scheme_create? +

Yes. Add a rate_limit block to the x402_payment_signature_exact_scheme_create 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 x402_payment_signature_exact_scheme_create completely? +

Set action: deny in the PolicyLayer policy for x402_payment_signature_exact_scheme_create. 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 x402_payment_signature_exact_scheme_create? +

x402_payment_signature_exact_scheme_create is provided by the Nano Currency MCP Server MCP server (kilkelly/nano-currency-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Nano Currency MCP Server tool call.

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

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