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ERC-20 Allowance Checker on Base
x402
ERC-20 Allowance Checker on Base is a paid API for AI agents from kr-x402-mvp.kgy5612.workers.dev, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-31).
Checks how much of an ERC-20 token a spender is approved to move from an owner's wallet on Base, with risk classification, exposure calculation, and ready-to-use revoke calldata.
Price / call$0.002
Success—
StatusUnknown
How this service works
ERC-20 approval check on Base: how much can spender move from owner? owner=0x..&spender=0x..[&token=0x.., default USDC][&amount=] -> allowance, unlimited flag, owner balance, exposure (min of allowance and balance), known spender label (Permit2, Uniswap, 1inch, 0x, Odos, Aerodrome), risk class, revoke_recommended + ready approve(spender,0) calldata, can_spend when amount= given. Use before transferFrom/swap, or to audit a wallet's dangerous approvals.
Output
A JSON object containing: current allowance (raw and human-readable), whether it is unlimited, owner's token balance, the effective exposure (min of allowance and balance), the known label for the spender (e.g. Uniswap Permit2, 1inch, Odos), a risk class (none/low/medium/high), whether revocation is recommended, ready-to-use approve(spender,0) calldata for revocation, can_spend boolean when amount is provided, and the block number at which the data was fetched.
Example use cases
Pre-swap approval safety check
“Before I execute this Uniswap swap, check if the Permit2 contract 0x000000000022D473030F116dDEE9F6B43aC78BA3 already has enough USDC allowance from my wallet 0xe4be4d0bd82d8e68203deff81f79ede0529f2617 to move 500 USDC, and whether that approval is risky.”
Wallet approval security audit
“Audit the USDC allowance that the Odos router 0xa669e7A0d4b3e4Fa48af2dE86BD4CD7126Be4e1 has on my wallet 0xabc1234000000000000000000000000000000001 — tell me the exposure, risk class, and give me revoke calldata if I should cancel it.”
Detect unlimited token approval
“Check if I accidentally gave unlimited USDC approval to the 1inch contract 0x1111111254EEB25477B68fb85Ed929f73A960582 from my wallet 0xdef0000000000000000000000000000000000002 on Base, and if so, give me the calldata to revoke it.”
Technical details
Endpoint
GEThttps://kr-x402-mvp.kgy5612.workers.dev/crypto/allowance?utm_source=zero.xyzWhen to prefer
Use this endpoint when your agent needs to verify ERC-20 token approvals on Base before executing swaps or transfers, or when auditing a wallet for dangerous unlimited approvals. It is purpose-built for Base with labeled spender recognition (Permit2, Uniswap, 1inch, 0x, Odos, Aerodrome) and includes pre-computed revoke calldata, making it faster than calling the blockchain directly. Prefer it over generic RPC calls when you need risk classification, exposure analysis, and actionable remediation in a single call.
Side effects
- Invalid owner or spender address format (not a 0x hex address) returns 400 error
- Unknown or non-ERC-20 token address may return error or zero values
- RPC timeout or Base node unavailability causes 503 or delayed response
- Missing required owner or spender parameters returns 400
- Amount parameter as non-numeric value causes validation error
- Payment not sent or insufficient USDC balance returns 402
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"risk": "none",
"block": 53250000,
"chain": "base",
"owner": "0xe4be4d0bd82d8e68203deff81f79ede0529f2617",
"token": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
"symbol": "USDC",
"spender": "0x000000000022D473030F116dDEE9F6B43aC78BA3",
"decimals": 6,
"exposure": 0,
"allowance": 0,
"revoke_tx": null,
"unlimited": false,
"allowance_raw": "0",
"owner_balance": 0.079,
"spender_label": "Uniswap Permit2",
"revoke_recommended": false
}
}Tags
x402
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