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x402 Chain Tools – ERC-20 Allowance Lookup
x402
x402 Chain Tools – ERC-20 Allowance Lookup is a paid API for AI agents from blockchain-api.x402-chain-tools.workers.dev, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-14).
Returns the ERC-20 token allowance granted by an owner address to a spender address on Base Mainnet.
Price / call$0.001
Success—
StatusUnknown
How this service works
Get the ERC-20 allowance from an owner to a spender.
Output
A JSON object containing the owner, token, network (eip155:8453 for Base Mainnet), and spender addresses, plus an allowance object with the raw value (as a string), decimal precision, human-formatted amount, and a boolean flag indicating whether the allowance is unlimited (max uint256).
Example use cases
Pre-trade DeFi approval check
“Before I swap tokens on Uniswap, can you check how much USDC (token 0x833589fcd6edb6e08f4c7c32d4f71b54bda02913) my wallet 0xAaBb...1234 has approved the Uniswap v3 router 0xE592427A0AEce92De3Edee1F18E0157C05861564 to spend on Base?”
DeFi protocol security audit
“Audit my token approvals — tell me how much of my WETH token at 0x4200000000000000000000000000000000000006 I've approved the Aave lending pool 0x...aave to spend from my address 0xMyWallet...5678 on Base Mainnet.”
Automated allowance monitoring agent
“Check whether the allowance my treasury address 0xTreasury...9999 has given to our payroll contract 0xPayroll...1111 for USDC on Base is still set to the expected amount, and alert me if it's zero or unlimited.”
Technical details
Endpoint
POSThttps://blockchain-api.x402-chain-tools.workers.dev/chain/allowanceWhen to prefer
Use this endpoint when you need to read ERC-20 token allowances on Base Mainnet specifically, without writing to the blockchain. Prefer this over generic RPC calls when you want a structured, formatted response that includes both raw and human-readable allowance values plus an unlimited-approval flag. Ideal for pre-flight checks before DeFi operations, security audits, and allowance monitoring workflows.
Side effects
- Invalid Ethereum address format returns a validation error
- Token contract address does not exist on Base returns zero or error
- Network congestion may slow RPC response
- Non-ERC-20 contract address may return unexpected data or error
- Missing required fields (owner, token, or spender) returns a 400 error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| owner | string | Token owner address. |
| token | string | ERC-20 token contract address on Base. |
| spender | string | Spender address. |
Output
Schema · Response
{
"type": "json",
"example": {
"ok": true,
"owner": "0x0000000000000000000000000000000000000001",
"token": "0x0000000000000000000000000000000000000002",
"network": "eip155:8453",
"spender": "0x0000000000000000000000000000000000000003",
"allowance": {
"raw": "0",
"decimals": 6,
"formatted": "0",
"unlimited": false
}
}
}Tags
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