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Ethereum ERC-20 Allowance Checker
x402
Ethereum ERC-20 Allowance Checker is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-21).
Returns the ERC-20 token allowance (raw and human-readable) that an owner has granted to a spender on Ethereum mainnet
Price / call$0.002
Success—
StatusUnknown
How this service works
Call when an agent needs ERC-20 allowance(owner, spender) on Ethereum, raw and human when decimals() is readable. Send token, owner, and spender. Read-only. No spend. Send JSON {"token":"0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48","owner":"0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045","spender":"0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48"}. Exact $0.002 USDC on Base. Try unpaid POST /v1/sandbox/eth-erc20-allowance first.
Output
Returns the allowance amount in two forms: raw (as the integer value from the contract) and human-readable (scaled by the token's decimals() value if readable), representing how many tokens the spender is authorized to transfer on behalf of the owner.
Example use cases
Pre-flight DeFi approval check
“Before I submit this swap, check how much USDC (0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48) my wallet 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045 has approved the Uniswap router 0xE592427A0AEce92De3Edee1F18E0157C05861564 to spend on Ethereum.”
Security audit of token approvals
“I need to audit token approvals — can you look up how much DAI (0x6B175474E89094C44Da98b954EedeAC495271d0F) the address 0xAbCd1234000000000000000000000000000000ab has allowed the Aave lending pool 0x7d2768dE32b0b80b7a3454c06BdAc94A69DDc7A9 to spend on Ethereum mainnet?”
Monitor staking contract allowance
“Check what the current WETH allowance is for owner 0x1234567890abcdef1234567890abcdef12345678 toward the staking contract 0xae7ab96520DE3A18E5e111B5EaAb095312D7fE84 on Ethereum — give me both the raw number and the human-readable amount.”
Technical details
Endpoint
POSThttps://agentshelf.syntexa.ch/v1/eth-erc20-allowance?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need a read-only, on-chain ERC-20 allowance lookup for Ethereum mainnet and want both raw and decimal-adjusted values in a single call. It's priced at $0.002 USDC per call and has a free sandbox at /v1/sandbox/eth-erc20-allowance for testing. Prefer it over building your own RPC calls when you need a simple, hosted allowance query without managing Ethereum node infrastructure.
Side effects
- Invalid or non-checksummed Ethereum address returns a 400 error
- Token contract address does not implement ERC-20 allowance() function returns an error
- Ethereum node unavailable or rate-limited returns a 503 or timeout
- Decimals not readable — returns raw value only without human-readable amount
- Payment not included or insufficient — returns 402 Payment Required; use sandbox endpoint first
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| owner | string | Token holder who granted the allowance. Example: 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045. EIP-55 or all one case. |
| token | string | ERC-20 contract on Ethereum mainnet. Example: 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48 (Circle USDC). allowance(owner, spender) is read-only. |
| spender | string | Account allowed to spend the tokens. Example: 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48. EIP-55 or all one case. |
Tags
x402
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