sign_message · Tenzro Ledger MCP: Risk & Policy

WHAT IT DOES

What sign_message does on Tenzro Ledger MCP

AI agents invoke sign_message to trigger actions in Tenzro Ledger MCP. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why sign_message needs a policy

Signing a message with a cryptographic wallet key is an execution operation that produces a cryptographic signature. While it doesn't directly transfer funds, it creates a signed artifact that could be used to authorize transactions, mandates, or other financial/sensitive operations.

From the tool's definition Sign a message with the auth-bound wallet (FROST-Ed25519 + ML-DSA-65 hybrid)

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

sign_message Rate-limited

sign_message stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "sign_message": {
      "limits": [
        {
          "counter": "sign_message_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Tenzro Ledger MCP, so you can run agents against it safely.

FAQ

Questions about sign_message

What does the sign_message tool do? +

Sign a message with the auth-bound wallet (FROST-Ed25519 + ML-DSA-65 hybrid). It is categorised as a Execute tool in the Tenzro Ledger MCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on sign_message? +

Register the Tenzro Ledger MCP server in PolicyLayer and add a rule for sign_message: 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 Tenzro Ledger MCP. Nothing to install.

What risk level is sign_message? +

sign_message is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit sign_message? +

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

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

sign_message is provided by the Tenzro Ledger MCP server (https://canton-mcp.tenzro.network/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.