contract__checkproxy

THE RISK

Low Risk

Why contract__checkproxy needs a policy

This tool retrieves and returns blockchain data (whether a contract is a proxy and its implementation address) without modifying, executing, or deleting anything. It is a read-only query against Etherscan's blockchain data APIs. Low severity because the information is already public on the blockchain, and misuse poses no financial or operational risk.

From the tool's definition Tool name contains 'check' and description states it 'checks if a contract is a proxy contract and returns the implementation address' — a pure query operation with no side effects.

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

POLICY

How to control contract__checkproxy

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

policy.json

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

contract__checkproxy 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 Etherscan MCP — 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 →

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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.
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MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
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FAQ

Questions about contract__checkproxy

What does the contract__checkproxy tool do? +

Checks if a contract is a proxy contract and returns the implementation address if it is. It is categorised as a Read tool in the Etherscan MCP MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on contract__checkproxy? +

Register the Etherscan MCP server in PolicyLayer and add a rule for contract__checkproxy: 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 Etherscan MCP. Nothing to install.

What risk level is contract__checkproxy? +

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

Can I rate-limit contract__checkproxy? +

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

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

contract__checkproxy is provided by the Etherscan MCP server (xiaok/etherscan-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Etherscan MCP tool call.

Start from Etherscan 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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