sendSignedTransaction

THE RISK

Critical Risk

Why sendSignedTransaction needs a policy

Sending a signed transaction to a blockchain is an irreversible financial/state-changing operation. It can transfer ETH, tokens, or trigger any contract interaction. Once broadcast and confirmed, transactions cannot be undone. This tool has critical blast radius as it can move funds or execute arbitrary on-chain operations on behalf of the wallet.

From the tool's definition Send a signed transaction to the blockchain network

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

POLICY

How to control sendSignedTransaction

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

policy.json

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

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

Create a free account and register MCP Ethers Wallet — 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

More MCP Ethers Wallet tools

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Go deeper

Govern MCP payment tools → Approval gates, spend caps, and per-identity scopes on every refund, payout, and charge your agents make.
Critical-risk tools in MCP Ethers Wallet → 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 →
PolicyLayer vs alternatives → How deterministic, per-call MCP policy compares with gateways, identity layers, and authorisation platforms.

FAQ

Questions about sendSignedTransaction

What does the sendSignedTransaction tool do? +

Send a signed transaction to the blockchain network. Returns transaction hash and receipt. It is categorised as a Financial tool in the MCP Ethers Wallet MCP Server, which means it involves financial transactions. Block by default and require explicit approval.

How do I enforce a policy on sendSignedTransaction? +

Register the MCP Ethers Wallet MCP server in PolicyLayer and add a rule for sendSignedTransaction: 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 MCP Ethers Wallet. Nothing to install.

What risk level is sendSignedTransaction? +

sendSignedTransaction 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 sendSignedTransaction? +

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

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

sendSignedTransaction is provided by the MCP Ethers Wallet MCP server (crazyrabbitltc/mcp-ethers-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every MCP Ethers Wallet tool call.

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

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