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Xerxes ERC20 Allowance Lookup
x402
Xerxes ERC20 Allowance Lookup is a paid API for AI agents from ari001.tailb4ac3a.ts.net, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-02).
Returns the uint256 allowance amount that a spender is approved to withdraw from an ERC20 token owner's account on Ethereum mainnet.
Price / call$0.003
Success—
StatusUnknown
How this service works
Returns the amount of ERC-20 tokens that a spender is allowed to withdraw from an owner's account. Provide token (ERC-20 contract address), owner (owner address), and spender (spender address). Query: token (ERC-20 contract, 0x + 40 hex), owner (0x + 40 hex), spender (0x + 40 hex).
Output
Returns a JSON object with an 'ok' boolean indicating success, a 'result' field containing the allowance as a uint256 decimal string, and metadata fields including 'chain', 'method', and 'service'. On failure, 'ok' is false and an 'error' string is present describing the issue.
Example use cases
DeFi pre-swap approval check
“Before I swap, can you check how much of my USDC (0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48) the 1inch router at 0x1111111254EEB25477B68fb85Ed929f73A960582 is currently allowed to spend from my wallet 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045?”
Token approval security audit
“I want to audit my wallet 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045 — can you check what allowance the Aave lending pool at 0x87870Bca3F3fD6335C3F4ce8392D69350B4fA4E2 has to spend my DAI tokens at 0x6B175474E89094C44Da98b954EedeAC495271d0F?”
Smart contract allowance verification
“Check if the spender contract 0x68b3465833fb72A70ecDF485E0e4C7bD8665Fc45 still has a nonzero allowance to pull WETH (0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2) from address 0xAb5801a7D398351b8bE11C439e05C5B3259aeC9B on Ethereum mainnet.”
Technical details
Endpoint
GEThttps://ari001.tailb4ac3a.ts.net/v1/ventures/ethereum_contract_abi_service/erc20_allowance?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need to read the current ERC20 allowance between a specific owner and spender on Ethereum mainnet without requiring a full node setup. Prefer this over general blockchain RPC calls when you want a clean, typed REST interface that returns the uint256 allowance as a human-readable decimal string with minimal setup. Ideal for pre-transaction validation, approval auditing, and DeFi automation workflows.
Side effects
- Invalid address format (not 0x + 40 hex) returns a validation error
- Contract address is not a valid ERC20 contract — call may revert or return unexpected data
- Network/RPC connectivity issues causing timeout or error response
- ok: false with error field when the on-chain call reverts
- Missing required query parameters (token, owner, or spender) results in 400-level error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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