# ERC-20 Allowance Lookup

> ERC-20 Allowance Lookup is a paid API for AI agents from twin.unykorn.org, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-02).

Returns how much a spender address is approved to transfer from an owner's ERC-20 token balance on a given EVM chain

## Facts

- Endpoint: POST https://twin.unykorn.org/erc20-allowance?utm_source=zero.xyz
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/erc-20-allowance-lookup-bb3bb2ae
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_yUA4IzOf0goU_Jmin55ZP

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability erc-20-allowance-lookup-bb3bb2ae -d '<json body>'
```

Example prompt: What's the current ERC-20 allowance that the Uniswap router (0x68b3465833fb72A70ecDF485E0e4C7bD8665Fc45) is approved to spend from my wallet (0xAb5801a7D398351b8bE11C439e05C5B3259aeC9B) for USDC (0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48) on Ethereum?

## When to prefer this

Use this endpoint when you need to programmatically check the current ERC-20 spending allowance between two specific addresses on any of 10 supported EVM chains without running your own node. It is ideal for pre-transaction approval validation, DeFi workflow automation, and security auditing of token approvals. It is preferable when you need a pay-per-call, no-subscription approach via the x402 protocol.

## Known failure modes

- Invalid Ethereum address format for owner, spender, or contract (must be 0x + 40 hex chars)
- Unsupported chain name — only ethereum, base, polygon, arbitrum, optimism, bsc, avalanche, gnosis, linea, scroll are accepted
- RPC node unavailable for the requested chain
- Payment failure via x402 protocol (insufficient USDC balance)
- Contract address is not a valid ERC-20 token

## How this service works

How much a spender is approved to move from an owner — Genesis402 / UnyKorn Operator Network

## Output

Returns a JSON object with ok status, the allowance type identifier, and a receipt containing a transaction hash, the USD cost of the call ($0.003), and a unique receipt ID — confirming how many tokens the spender is approved to move from the owner for the given ERC-20 contract on the specified chain.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "params": {
   "type": "object",
   "properties": {
    "chain": {
     "enum": [
      "ethereum",
      "base",
      "polygon",
      "arbitrum",
      "optimism",
      "bsc",
      "avalanche",
      "gnosis",
      "linea",
      "scroll"
     ],
     "type": "string"
    },
    "owner": {
     "type": "string",
     "pattern": "^0x[0-9a-fA-F]{40}$"
    },
    "spender": {
     "type": "string",
     "pattern": "^0x[0-9a-fA-F]{40}$"
    },
    "contract": {
     "type": "string",
     "pattern": "^0x[0-9a-fA-F]{40}$"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "ok": true,
  "type": "erc20-allowance",
  "receipt": {
   "tx_hash": "0x<64hex>",
   "amount_usd": 0.003,
   "receipt_id": "g402-<16hex>"
  },
  "generated_at": "<iso8601>"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/erc-20-allowance-lookup-bb3bb2ae/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from twin.unykorn.org](https://www.zero.xyz/host/twin.unykorn.org/llms.txt)