7702 Sweeper Check MCP Server

7702 Sweeper Check

Does your EVM wallet have an EIP-7702 delegation you didn't set?

Since Ethereum's Pectra upgrade, one signature can attach contract code to an ordinary wallet (EIP-7702). Smart-wallet upgrades use this legitimately. Drainers use it to install sweepers: tiny contracts that forward anything sent to your wallet straight to the attacker.

This project checks 8 chains at once: Ethereum, Base, BNB Chain, Arbitrum, OP, Polygon, Gnosis and Unichain.

• Web (free): https://sweeper-check.nextill-pos.workers.dev
• CLI (free): npx devx-7702-check 0xYourAddress
• MCP server for AI agents (free): remote https://sweeper-check.nextill-pos.workers.dev/mcp, or local npx devx-7702-check mcp
• JSON API (free): GET /api/basic?address=0x...
• Full report (paid, 0.01 USDC on Base via x402): GET /v1/check?address=0x..[,0x..], 1–20 addresses per call. It adds:
  • a delegate bytecode heuristic (a small contract with a hard-coded forwarding address = the sweeper shape);
  • source-verification status (Sourcify / Blockscout);
  • a risk level and what to do. You're charged only after the report is produced. Humans can pay with a browser wallet on the web page: you sign one USDC authorization and pay no gas.

Read-only. It never asks for or touches private keys or seed phrases.

How detection works

A 7702-delegated account's code is exactly 0xef0100 ‖ <20-byte delegate address>. The free check reads eth_getCode and the nonce on each chain. The paid report then fetches the delegate's bytecode and walks the opcodes (skipping PUSH data):

• PUSH20 constants other than your own address and the ERC-4337 EntryPoints, combined with CALL, in a contract under 1.2 KB → high (sweeper pattern).
• SELFBALANCE + CALL + a hard-coded address → medium.
• Verified source or ERC-4337 smart-account shape → low.
• Otherwise → medium/unknown.

These are heuristics, not guarantees. If a delegation you didn't create shows up, treat the key as compromised and move funds to a new wallet made on a clean device. Re-delegating to 0x0 doesn't help if an attacker holds the key.

CLI

npx devx-7702-check 0xabc... 0xdef...    # exit code 0 = none, 2 = delegation found, 1 = error
npx devx-7702-check 0xabc... --json

MCP

Claude Desktop / Cursor config:

{ "mcpServers": { "7702-sweeper-check": { "url": "https://sweeper-check.nextill-pos.workers.dev/mcp" } } }

or stdio: { "command": "npx", "args": ["-y", "devx-7702-check", "mcp"] }

Tools: check_7702_delegation(address), full_report_info().

x402 (agents)

GET /v1/check?address=... returns 402 with a PAYMENT-REQUIRED header (x402 v2, scheme exact, network eip155:8453, USDC 0x8335…2913, amount 10000 = 0.01 USDC). Pay with any x402 client. Discovery: /.well-known/x402.json, /openapi.json. Terms: /terms.

Layout

• worker/: Cloudflare Worker source (page, free API, x402 paid route, remote MCP)
• cli/: the npm package devx-7702-check (CLI + stdio MCP server)

Made by DevX. MIT.

Guide

• What is an EIP-7702 sweeper?
• Related free tool: Crypto Link Check — is that wallet or exchange link real?
• Related free tool: Address Poisoning Check — is the address you are about to pay a poisoned lookalike?