send-transaction

THE RISK

Critical Risk

Why send-transaction needs a policy

Sending blockchain transactions is a financial operation that can transfer funds or commit financial obligations on-chain. This is irreversible once confirmed and has a critical blast radius if misused by an AI agent, as it could drain wallet funds or execute unintended financial operations.

From the tool's definition 'Send transactions to networks' — sending blockchain transactions moves cryptocurrency or triggers financial smart contract operations

Documented attack patterns abuse exactly the kind of access send-transaction gives an agent:

POLICY

How to control send-transaction

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

policy.json

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

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

Create a free account and register MetaMask MCP — 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 MetaMask MCP tools

Execute deploy-contract Deploy a contract to the network, given bytecode, and constructor arguments. Execute call Executing a new message call immediately without submitting a transaction to the network. Execute sign-message Sign a message. Execute switch-chain Switch the target chain. Execute write-contract Execute a write function on a contract. Write disconnect Disconnect the wallet. Read wait-for-transaction-receipt Waits for the transaction to be included on a block, and then returns the transaction rece Other wait-seconds Wait the given seconds.

All 29 MetaMask MCP tools →

Financial tools on other servers

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Go deeper

Critical-risk tools in MetaMask MCP → 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 send-transaction

What does the send-transaction tool do? +

Send transactions to networks. It is categorised as a Financial tool in the MetaMask MCP MCP Server, which means it involves financial transactions. Block by default and require explicit approval.

How do I enforce a policy on send-transaction? +

Register the MetaMask MCP server in PolicyLayer and add a rule for send-transaction: 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 MetaMask MCP. Nothing to install.

What risk level is send-transaction? +

send-transaction 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 send-transaction? +

Yes. Add a rate_limit block to the send-transaction 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 send-transaction completely? +

Set action: deny in the PolicyLayer policy for send-transaction. 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 send-transaction? +

send-transaction is provided by the MetaMask MCP server (xiawpohr/metamask-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every MetaMask MCP tool call.

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

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