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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 api.api-agent-ia.ch, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-24).
Returns the ERC-20 token allowance a spender is approved to use from an owner's wallet on Base mainnet, flagging unlimited approvals.
Price / call$0.002
Success—
StatusUnknown
How this service works
Is a token approval already granted? Returns the ERC-20 allowance an owner gave a spender on Base, raw and formatted, and flags unlimited approvals ($0.002 per call).
Output
Returns a JSON object containing the owner address, token address, token symbol, spender address, and the formatted allowance amount the spender is approved to use. Unlimited approvals are flagged with a special indicator.
Example use cases
Pre-swap approval check for DeFi
“I'm about to swap USDC for ETH on a Base DEX — can you check if my wallet 0xAbCd...1234 has already approved the router contract 0x3fC9...5678 to spend USDC at 0xd9aA...ef01 on Base, and tell me how much is approved?”
Detect unlimited token approval risk
“Can you check whether my address 0xBEEF...cafe has granted an unlimited approval to the contract 0xDEAD...beef for the USDT token 0x4200...0006 on Base? I want to know if I should revoke it.”
Audit DeFi protocol allowances before interaction
“Before I deposit into this lending protocol at 0x1234...abcd, check if my wallet 0x5678...dcba already has an approval set for DAI token 0x50c5...725D on Base so I don't have to approve again.”
Technical details
Endpoint
GEThttps://api.api-agent-ia.ch/allowance?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need to check an existing ERC-20 token approval on Base mainnet before initiating a DeFi transaction such as a swap, deposit, or transfer. It is ideal for pre-flight checks in DeFi automation agents to avoid unnecessary on-chain approval transactions. Prefer this over general blockchain explorers when you want a structured, agent-consumable response with formatted allowance and unlimited-approval detection.
Side effects
- Invalid 0x address format for token, owner, or spender returns an error
- Token address is not a valid ERC-20 contract on Base returns an error or zero allowance
- Network issues with Base RPC may cause timeouts
- Querying an address with no approval returns allowance of 0
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"owner": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
"token": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
"reseau": "base",
"symbol": "USDC",
"spender": "0x000000000022D473030F116dDEE9F6B43aC78BA3",
"decimals": 6,
"illimitee": false,
"allowance_brut": "0",
"allowance_formate": "0"
}
}Tags
x402
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