AI agents call formatUnits to retrieve information from MCP Ethers Wallet without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
formatUnits is a standard ethers.js utility that converts blockchain values to human-readable format. It performs no state changes, does not execute transactions, and has no destructive or financial implications. The low severity reflects that misuse would only produce incorrect output formatting, not data loss or unauthorized transactions.
From the tool's definition Tool name 'formatUnits' suggests a utility function for formatting numerical values (likely converting wei to readable Ether units). The empty description provides no evidence of side effects, data modification, or financial operations.
Documented attack patterns abuse exactly the kind of access formatUnits gives an agent:
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 formatUnits:
{
"version": "1",
"default": "deny",
"tools": {
"formatUnits": {}
}
}formatUnits is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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formatUnits. It is categorised as a Read tool in the MCP Ethers Wallet MCP Server, which means it retrieves data without modifying state.
Register the MCP Ethers Wallet MCP server in PolicyLayer and add a rule for formatUnits: 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.
formatUnits is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the formatUnits 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.
Set action: deny in the PolicyLayer policy for formatUnits. 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.
formatUnits 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.
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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69 MCP Ethers Wallet tools catalogued and risk-classified — across an index of 43,000+ MCP servers.