eth_signTransaction · Privy MCP Server MCP: Risk & Policy

WHAT IT DOES

What eth_signTransaction does on Privy MCP Server

AI agents invoke eth_signTransaction 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 eth_signTransaction needs a policy

Signing a transaction is a precursor to blockchain execution. While signing alone doesn't broadcast the transaction, it authorizes and prepares an Ethereum transaction for submission, which can have financial/irreversible consequences.

From the tool's definition Sign a transaction using the eth_signTransaction method with a specified wallet

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

eth_signTransaction Rate-limited

eth_signTransaction 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": {
    "eth_signTransaction": {
      "limits": [
        {
          "counter": "eth_signtransaction_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 eth_signTransaction

What does the eth_signTransaction tool do? +

Sign a transaction using the eth_signTransaction 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 eth_signTransaction? +

Register the Privy MCP Server MCP server in PolicyLayer and add a rule for eth_signTransaction: 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 eth_signTransaction? +

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

Can I rate-limit eth_signTransaction? +

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

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

eth_signTransaction 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.