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Base ERC-20 Allowance Checker
x402
Base ERC-20 Allowance Checker is a paid API for AI agents from onchaincheck.dev, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-29).
Returns the ERC-20 token allowance a spender has from an owner on Base, including whether it's unlimited, the owner's balance, and the spendable amount right now.
Price / call$0.005
Success—
StatusUnknown
How this service works
ERC-20 allowance on Base: how much a spender may transfer from an owner, whether the approval is effectively unlimited, the owner's balance, and the amount the spender could move right now.
Output
A JSON object containing the token symbol, the raw and human-readable allowance, a boolean indicating whether the approval is effectively unlimited, the owner's current token balance, and the amount the spender could transfer right now (min of allowance and balance), all scoped to the Base network.
Example use cases
DeFi approval security audit
“I want to audit my Base wallet approvals — can you check how much the Uniswap Universal Router (0x3fC91A3afd70395Cd496C647d5a6CC9D4B2b7FAD) is allowed to spend of my USDC (0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) from my address 0x698229f40EF287c4B470813e95429f8d764E8054, and tell me if the approval is unlimited?”
Pre-trade allowance verification
“Before my trading bot executes a swap, check if the Aerodrome router 0x6Cb442acF35158D5eDa88fe602221b67A400D89 has enough allowance to move at least 500 USDC from my wallet 0xABC1234567890abcdef1234567890abcdef12345 on Base — use token address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913.”
Revoke candidate identification
“I think I left a large approval open on Base months ago. Can you look up how much the old contract 0xDEF9876543210fedcba9876543210fedcba98765 is approved to spend of my WETH (0x4200000000000000000000000000000000000006) from my address 0x1111111111111111111111111111111111111111, and confirm whether it's an unlimited allowance?”
Technical details
Endpoint
GEThttps://onchaincheck.dev/base/allowance?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need to verify ERC-20 token approvals specifically on the Base network. It provides a complete picture in a single call — allowance, unlimited flag, owner balance, and actual spendable amount — saving multiple on-chain RPC calls. Prefer it over generic RPC queries when you need structured, parsed output ready for agent decision-making, especially for DeFi workflows, security audits, or pre-trade checks on Base.
Side effects
- Invalid address format (not matching 0x[40 hex chars]) returns a validation error
- Token address is not a valid ERC-20 contract on Base — may return zero values or an error
- No approval exists — returns allowance of 0 and spendableNow of 0, not an error
- Network RPC issues on Base may cause timeouts or incomplete data
- Calling with an EOA address as the token returns invalid/empty results
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"raw": "0",
"chain": "base",
"owner": "0x698229f40EF287c4B470813e95429f8d764E8054",
"token": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
"symbol": "USDC",
"spender": "0x000000000022D473030F116dDEE9F6B43aC78BA3",
"allowance": "0",
"unlimited": false,
"ownerBalance": "0",
"spendableNow": "0"
}
}Tags
x402
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