# ERC-20 Token Allowance Lookup (Vextorium)

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

Looks up how much of an ERC-20 token a spender is approved to transfer from an owner's wallet, and flags whether the approval is unlimited.

## Facts

- Endpoint: POST https://api.vextorium.com/permiso-token-pago?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-token-allowance-lookup-vextorium-d7800a9a
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_uKmPCrcKxI0kp36BlKn3Q

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-vextorium-d7800a9a -d '<json body>'
```

Example prompt: Check how much USDC (contract 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48) the Uniswap v3 router (0xE592427A0AEce92De3Edee1F18E0157C05861564) is allowed to spend from my wallet (0xAbCd1234...5678) on Ethereum, and tell me if it's an unlimited approval.

## When to prefer this

Choose this endpoint when you need a direct on-chain read of the ERC-20 allowance between a specific owner and spender pair — especially when you want automatic detection of unlimited approvals (max uint256). It supports five major EVM networks (Base, Ethereum, Arbitrum, Optimism, Polygon) in a single API, making it ideal for cross-chain wallet security audits, DeFi approval monitoring, or pre-transaction permission checks without needing your own RPC infrastructure.

## Known failure modes

- Invalid or non-checksummed contract/wallet address returns an error
- Token address is not a valid ERC-20 contract on the specified network
- Network enum value not recognized (must be base, ethereum, arbitrum, optimism, or polygon)
- No allowance set (returns 0) which may be confused with an error
- RPC node timeout or network congestion causing a slow or failed read
- Missing required fields (token, propietario, gastador) causes validation error

## How this service works

ERC-20 allowance lookup: how much a spender can move from an owner's balance, flagging unlimited approvals.

## Output

Returns the approved allowance amount (as a number), a boolean flag indicating whether the approval is unlimited (max uint256), plus echoed fields for the network, token address, spender address, owner address, and an optional note field for additional context.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "required": [
      "token",
      "propietario",
      "gastador"
     ],
     "properties": {
      "red": {
       "enum": [
        "base",
        "ethereum",
        "arbitrum",
        "optimism",
        "polygon"
       ],
       "type": "string",
       "description": "EVM network (default base)"
      },
      "token": {
       "type": "string",
       "description": "Token contract address"
      },
      "gastador": {
       "type": "string",
       "description": "Spender (contract) address"
      },
      "propietario": {
       "type": "string",
       "description": "Owner wallet address"
      }
     }
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json",
      "form-data",
      "text"
     ],
     "type": "string"
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "red": {
       "type": [
        "string",
        "null"
       ]
      },
      "nota": {
       "type": [
        "string",
        "number",
        "boolean",
        "object",
        "array",
        "null"
       ]
      },
      "token": {
       "type": [
        "string",
        "null"
       ]
      },
      "permiso": {
       "type": [
        "number",
        "null"
       ]
      },
      "contrato": {
       "type": [
        "string",
        "null"
       ]
      },
      "gastador": {
       "type": [
        "string",
        "null"
       ]
      },
      "ilimitado": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "propietario": {
       "type": [
        "string",
        "null"
       ]
      }
     }
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "red": "base",
  "nota": null,
  "token": "USDC",
  "permiso": 0,
  "contrato": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
  "gastador": "0x3d4e44Eb1374240CE5F1B871ab261CD16335B76a",
  "ilimitado": false,
  "propietario": "0xb9f06D2734B7E9D7b21B64C4D8b95bd774b71aCf"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/erc-20-token-allowance-lookup-vextorium-d7800a9a/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)