formatEther

THE RISK

Low Risk

Why formatEther needs a policy

formatEther is a pure utility function for converting/formatting blockchain numeric values. It reads data without modifying state, executing code with external side effects, deleting data, or moving funds. Even in a wallet context, formatting functions are non-destructive data operations. Confidence is slightly reduced due to the empty description, but the name strongly implies a read-only transformation.

From the tool's definition Tool name 'formatEther' suggests a utility function that converts or formats Ethereum values (likely wei to ether).

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

POLICY

How to control formatEther

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 formatEther:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "formatEther": {}
  }
}

formatEther is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

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.

CAP THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More MCP Ethers Wallet tools

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All 69 MCP Ethers Wallet tools →

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Go deeper

Roll out MCP under one policy → Per-person scoped tokens, one central policy, and full audit across every server your team connects.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →
PolicyLayer vs alternatives → How deterministic, per-call MCP policy compares with gateways, identity layers, and authorisation platforms.

FAQ

Questions about formatEther

What does the formatEther tool do? +

formatEther. It is categorised as a Read tool in the MCP Ethers Wallet MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on formatEther? +

Register the MCP Ethers Wallet MCP server in PolicyLayer and add a rule for formatEther: 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 formatEther? +

formatEther is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit formatEther? +

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

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

formatEther 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.

CHECK YOUR STACK →