lookup_ens_address

THE RISK

Low Risk

Why lookup_ens_address needs a policy

This tool performs a read-only lookup of ENS (Ethereum Name Service) reverse resolution, converting an Ethereum address to its associated ENS name. It retrieves data from the blockchain without side effects, making it a Read category tool.

From the tool's definition Tool description states 'Lookup the ENS name for an Ethereum address (reverse resolution)' - a query operation that retrieves publicly available blockchain data without modifying state or executing code.

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

POLICY

How to control lookup_ens_address

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

policy.json

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

lookup_ens_address 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 EVM MCP Server — 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

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Go deeper

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 →

FAQ

Questions about lookup_ens_address

What does the lookup_ens_address tool do? +

Lookup the ENS name for an Ethereum address (reverse resolution). It is categorised as a Read tool in the EVM MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on lookup_ens_address? +

Register the EVM MCP Server MCP server in PolicyLayer and add a rule for lookup_ens_address: 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 EVM MCP Server. Nothing to install.

What risk level is lookup_ens_address? +

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

Can I rate-limit lookup_ens_address? +

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

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

lookup_ens_address is provided by the EVM MCP Server MCP server (mcpdotdirect/evm-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every EVM MCP Server tool call.

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

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