# ERC-20 Token Allowance Lookup

> ERC-20 Token Allowance Lookup is a paid API for AI agents from api.vextorium.com, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-19).

Returns how many tokens a spender is approved to move from an owner's wallet on a given EVM network, flagging whether the approval is unlimited.

## Facts

- Endpoint: POST https://api.vextorium.com/v1/token-allowance?utm_source=zero.xyz
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-19
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/erc-20-token-allowance-lookup-40c1cd58
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_fI8kQohWPCGNmlkIzQ68l

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-token-allowance-lookup-40c1cd58 -d '<json body>'
```

Example prompt: Check the USDC allowance on Base for owner wallet 0xb9f06D2734B7E9D7b21B64C4D8b95bd774b71aCf and spender 0x3d4e44Eb1374240CE5F1B871ab261CD16335B76a — I want to know if it's unlimited or the exact amount approved.

## When to prefer this

Use this endpoint when you need a fast, single on-chain read of an ERC-20 allowance without running your own blockchain node or writing contract call code. It is ideal for wallet security dashboards, pre-swap checks, and approval auditing workflows across Base, Ethereum, Arbitrum, Optimism, and Polygon. Prefer this over general-purpose blockchain RPC tools when you specifically need the allowance amount and an explicit unlimited-approval flag in a structured JSON response.

## Known failure modes

- Invalid or malformed wallet/contract addresses return an error
- Unsupported network returns a validation error
- Token contract address not found on the specified network may return null values
- RPC node timeout causes a failed lookup
- Missing required fields (token, owner, spender) returns a schema validation error

## How this service works

558 pay-per-call data APIs for AI agents: Solana and EVM on-chain data, tokenized stocks, DeFi, Hyperliquid, economy and official statistics, FX, validation, web and developer tools. Pay in USDC via x402.

## Output

Returns a JSON object with the token symbol, contract address, network, owner and spender addresses, the numeric allowance (permission), and a boolean 'unlimited' flag indicating whether the approval is set to the maximum uint256 value. Also includes an optional note field.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "owner": {
   "type": "string",
   "description": "Owner wallet address"
  },
  "token": {
   "type": "string",
   "description": "Token contract address"
  },
  "network": {
   "enum": [
    "base",
    "ethereum",
    "arbitrum",
    "optimism",
    "polygon"
   ],
   "type": "string",
   "description": "EVM network (default base)"
  },
  "spender": {
   "type": "string",
   "description": "Spender (contract) address"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "note": null,
  "owner": "0xb9f06D2734B7E9D7b21B64C4D8b95bd774b71aCf",
  "token": "USDC",
  "network": "base",
  "spender": "0x3d4e44Eb1374240CE5F1B871ab261CD16335B76a",
  "contract": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
  "unlimited": false,
  "permission": 0
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/erc-20-token-allowance-lookup-40c1cd58/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.vextorium.com](https://www.zero.xyz/host/api.vextorium.com/llms.txt)