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ERC20 Allowance Lookup (eth_call)
x402
ERC20 Allowance Lookup (eth_call) is a paid API for AI agents from api.onesource.io, paid per call via x402, $0.003/call, status unknown (last checked 2026-09-15).
Returns how many tokens a spender is approved to transfer from an owner's wallet for a given ERC20 token contract on Ethereum or Sepolia.
Price / call$0.003
Success—
StatusUnknown
How this service works
ERC20 allowance via allowance (eth_call) - how much a spender is approved to move from an owner's wallet
Output
The approved token allowance — i.e. the maximum number of token units the spender is permitted to transfer from the owner's address — returned as a numeric value in the token's base units (e.g. USDC uses 6 decimals).
Example use cases
Example prompt
“How much USDC (0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48) is the Uniswap v3 router (0xE592427A0AEce92De3Edee1F18E0157C05861564) approved to spend from my wallet 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045 on Ethereum mainnet?”
Technical details
Endpoint
GEThttps://api.onesource.io/api/chain/allowanceWhen to prefer
Use this endpoint when you need to read the current ERC20 token allowance between a specific owner-spender pair on Ethereum mainnet or Sepolia testnet. Ideal for DeFi automation, pre-transaction approval checks, or auditing wallet approvals without needing to run your own Ethereum node. Prefer this over general-purpose RPC providers when you want a simple REST GET interface with x402 micropayment access.
Side effects
- Invalid Ethereum address format for owner, spender, or token returns a 400 validation error
- Unsupported network value (anything other than 'ethereum' or 'sepolia') returns an error
- Token address is not a valid ERC20 contract (no allowance function) may return zero or an RPC error
- Network congestion or node unavailability may cause timeouts
- Missing required parameter (owner, spender, or token) returns a 422 or 400 error
Input
{
"owner": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
"token": "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
"network": "ethereum",
"spender": "0xE592427A0AEce92De3Edee1F18E0157C05861564"
}Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
{
"data": {
"name": "USD Coin",
"owner": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
"token": "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
"symbol": "USDC",
"spender": "0xE592427A0AEce92De3Edee1F18E0157C05861564",
"decimals": 6,
"allowance": "0"
},
"meta": {
"endpoint": "/api/chain/allowance",
"request_id": "8f42928bfd49c63e"
}
}Schema · Response
{
"type": "json",
"example": {
"data": {
"name": "Tether USD",
"owner": "0xd8da6bf26964af9d7eed9e03e53415d37aa96045",
"token": "0xdac17f958d2ee523a2206206994597c13d831ec7",
"symbol": "USDT",
"spender": "0x6b175474e89094c44da98b954eedeac495271d0f",
"decimals": 6,
"allowance": "115792089237316195423570985008687907853269984665640564039457584007913129639935"
},
"meta": {
"endpoint": "/api/chain/allowance",
"cost_usdc": "0.001",
"request_id": "00000000abcdef01",
"payment_chain": "base",
"payment_token": "USDC"
}
}
}Tags
x402
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