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Base ERC-20 Allowance Checker
x402
Base ERC-20 Allowance Checker is a paid API for AI agents from ca-tax-api-mainnet.lxtap.workers.dev, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-23).
Returns the ERC-20 token allowance a spender has from an owner on Base, including whether it is effectively unlimited, the owner's current balance, and the spendable amount right now.
Price / call$0.005
Success—
StatusUnknown
How this service works
Pay-per-call data for AI agents, paid in USDC on Base with x402: token risk checks (rug check) on Base, Ethereum, Arbitrum, Optimism, Polygon and Solana, onchain reads (balances, transactions, gas, contracts, NFTs, whale trades, new pools, ENS and Basenames), ECB exchange rates, and Canadian sales tax and business days.
Output
Returns the raw allowance granted by the owner to the spender, a boolean or flag indicating whether the approval is effectively unlimited (e.g. max uint256), the owner's current token balance, and the effective spendable amount (the lesser of allowance and balance) — all for the specified ERC-20 token on Base mainnet.
Example use cases
DeFi protocol approval audit
“On Base, check the token allowance for USDC contract 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 — I want to know how much spender 0x3fC91A3afd70395Cd496C647d5a6CC9D4B2b7FAD is approved to transfer from my wallet 0xAbCd1234AbCd1234AbCd1234AbCd1234AbCd1234, whether that approval is unlimited, and how much they could actually move right now.”
Security check before revoking approval
“Before I revoke approvals, can you pull the current allowance on Base for token 0x4200000000000000000000000000000000000006 where spender 0x2626664c2603336E57B271c5C0b26F421741e481 was approved by owner 0xDeAd0000DeAd0000DeAd0000DeAd0000DeAd0000? Tell me if it's unlimited and how much they could move given my balance.”
Verify swap router authorization
“I want to confirm my swap router on Base has the right authorization — check allowance for token 0x50c5725949A6F0c72E6C4a641F24049A917DB0Cb, owner 0x1234567890abcdef1234567890abcdef12345678, spender 0x4752ba5DBc23f44D87826276BF6Fd6b1C372aD24, and let me know the spendable amount versus my actual balance.”
Technical details
Endpoint
GEThttps://ca-tax-api-mainnet.lxtap.workers.dev/base/allowance?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need to inspect ERC-20 token approvals specifically on Base mainnet — particularly when you want to know not just the raw allowance but also whether it is effectively unlimited and how much the spender can actually transfer given the owner's real balance. Prefer this over generic blockchain explorers when you need a structured, machine-readable response suitable for automated DeFi workflows, security audits, or approval management agents.
Side effects
- Invalid or malformed Ethereum address format returns a validation error
- Token address is not a valid ERC-20 contract on Base — returns an error or zero values
- Network or RPC timeout causes a 5xx response
- Owner or spender address not found on-chain returns zero allowance and zero balance
- Missing required query parameters (token, owner, spender) returns a 400 bad request
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"raw": "0",
"chain": "base",
"owner": "0x698229f40EF287c4B470813e95429f8d764E8054",
"token": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
"symbol": "USDC",
"spender": "0x000000000022D473030F116dDEE9F6B43aC78BA3",
"allowance": "0",
"unlimited": false,
"ownerBalance": "0",
"spendableNow": "0"
}
}Tags
x402
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