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Base ERC20 Allowance Lookup
x402
Base ERC20 Allowance Lookup is a paid API for AI agents from x402.agentindex.world, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-10).
Reads the ERC20 token allowance on Base mainnet — how many tokens a spender is approved to transfer from an owner's wallet — via an eth_call to the allowance(owner,spender) function.
Price / call$0.003
Success—
StatusUnknown
How this service works
ERC20 spending allowance an owner has granted a spender on Base mainnet, via allowance(owner,spender).
Output
Returns the current ERC20 allowance as an integer (or formatted token amount) representing the number of tokens the spender is approved to transfer from the owner's balance for the specified token contract on Base mainnet. A value of zero means no approval exists; a very large value (e.g. max uint256) typically indicates an unlimited approval.
Example use cases
Pre-swap approval verification
“Before I swap on Aerodrome on Base, can you check if the router 0xcF77a3Ba9A5CA399B7c97c74d54e5b1Beb874E43 is approved to spend my USDC (0xd9aAEc86B65D86f6A7B5B1b0c42FFA531710b6CA) from my wallet 0xAbCd1234567890AbCd1234567890AbCd12345678?”
DeFi security audit of token approvals
“I want to audit my wallet 0xAbCd1234567890AbCd1234567890AbCd12345678 — check the allowance that the Aave v3 pool 0xA238Dd8sFs3a5a7bF7a3C7C4e2C1D8F9a3B2E1A on Base has to spend my WETH token at 0x4200000000000000000000000000000000000006.”
Agent verifying spending limit before payment
“My agent is about to trigger a Base transaction — first check whether the payment contract 0x1111111111111111111111111111111111111111 has enough allowance to move DAI (0x50c5725949A6F0c72E6C4a641F24049A917DB0Cb) from the treasury wallet 0xDeAdBeEf1234567890DeAdBeEf1234567890DeAd.”
Technical details
Endpoint
GEThttps://x402.agentindex.world/base/allowance?utm_source=zero.xyzWhen to prefer
Use this endpoint when you specifically need to read ERC20 token allowances on Base mainnet without managing your own RPC node or web3 infrastructure. Ideal for AI agents that need on-chain approval state before executing or recommending DeFi actions on Base. Prefer this over a generic Ethereum allowance checker when the user is operating on Base (Coinbase L2). The pay-per-call x402 model makes it cost-efficient for low-frequency spot checks without subscription overhead.
Side effects
- Invalid or non-checksummed Ethereum address for owner, spender, or token — returns error or unexpected result
- Token address is not a valid ERC20 contract on Base mainnet — eth_call may revert or return empty
- Base RPC node downtime or network congestion causing timeout
- Payment failure (x402) if insufficient USDC balance for the $0.003 fee
- Querying a token that exists on Ethereum mainnet but not on Base — returns zero allowance misleadingly
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| owner | string | |
| token | string | |
| spender | string |
Tags
x402
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