personal_sign · Privy MCP Server MCP: Risk & Policy

WHAT IT DOES

What personal_sign does on Privy MCP Server

AI agents invoke personal_sign to trigger actions in Privy MCP Server. 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 personal_sign needs a policy

personal_sign triggers a cryptographic signing operation using a blockchain wallet. While it doesn't move funds directly, signing messages can authorize transactions, authenticate to dApps, or be used in phishing/approval schemes. It is an external operation with real-world consequences depending on what is being signed, placing it in Execute.

From the tool's definition Sign a message using the personal_sign method with a specified wallet

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

personal_sign Rate-limited

personal_sign 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": {
    "personal_sign": {
      "limits": [
        {
          "counter": "personal_sign_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 Privy MCP Server, so you can run agents against it safely.

FAQ

Questions about personal_sign

What does the personal_sign tool do? +

Sign a message using the personal_sign method with a specified wallet. It is categorised as a Execute tool in the Privy MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on personal_sign? +

Register the Privy MCP Server MCP server in PolicyLayer and add a rule for personal_sign: 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 Privy MCP Server. Nothing to install.

What risk level is personal_sign? +

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

Can I rate-limit personal_sign? +

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

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

personal_sign is provided by the Privy MCP Server MCP server (privy-io/privy-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.