approval-guardian 🛡️

Find the token approvals draining your wallet — and get the revoke calldata.

approval-guardian is an MCP server and a pay-per-call x402 HTTP API. Give it a wallet address + chain and it returns a CLEAN / REVIEW / AT_RISK verdict listing every active ERC-20 approval, worst first, with the exact approve(spender, 0) calldata to revoke each one.

Unlimited token approvals are the #1 way DeFi wallets get drained — a single bad approve() lets a spender move your entire balance of that token, forever, in one transaction.

⚠️ Read-only risk screen, not financial advice. approval-guardian never holds a key and never moves funds. Revoking is a transaction you sign. Absence of findings is not proof of safety.

Why it exists (the moat)

To know what a wallet has approved, an agent that "just reads the chain" must:

1. Pull every ERC-20 Approval log the wallet ever emitted (paginated eth_getLogs with the right topic0 + owner topic, respecting per-RPC block-range caps).

2. For each (token, spender) pair, read the LIVE allowance() — because a later approve(0) or a spend may have changed it. Stale logs lie.

3. Read each token's decimals/symbol to turn a raw allowance into a human amount.

4. Classify the spender: is it a contract at all? a plain wallet (EOA)? an EIP-1967 upgradeable proxy whose code can be swapped behind your approval? a recognised router/permit/locker?

5. Score the blast radius and order the revokes.

approval-guardian batches all of that over public RPCs and returns one prioritized report. That live aggregation — not a static answer — is what an agent pays for.

Related MCP server: chain-signer

What it catches

Use as an MCP server (free)

{
  "mcpServers": {
    "approval-guardian": { "command": "npx", "args": ["-y", "approval-sentinel-mcp"] }
  }
}

Tools:

• check_approvals — full approval-risk report. Params: chain, wallet, deep (optional, full history).

• revoke_plan — just the ordered list of risky approvals + revoke calldata. Params: chain, wallet, minRisk.

Or connect over HTTP at POST /mcp.

Free HTTP API

GET /check?chain=base&wallet=0xYourWallet
GET /check?chain=ethereum&wallet=0x...

Returns the active approvals worst-first, each with revokeCalldata.

Pay-per-call (x402)

The /pro/* routes are gated by x402. Your agent pays $0.20 USDC per call automatically — no sign-up, no API key. The pro scan covers full on-chain history; settles on-chain (Base) to the operator wallet.

GET /pro/check?chain=base&wallet=0x...        # 402 → pay → deep report
GET /pro/revoke_plan?chain=base&wallet=0x...

Chains

Ethereum · Base · BSC · Polygon · Arbitrum — all via public, key-free RPCs.

Part of the guardian set

npm-guardian · contract-auditor · rug-check · approval-guardian

Source & docs: github.com/Baneado98/approval-guardian · MIT