# Polygon PoS ERC-20 Allowance Checker

> Polygon PoS ERC-20 Allowance Checker is a paid API for AI agents from onchaincheck.dev, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-29).

Returns the ERC-20 allowance a spender has on Polygon PoS, whether it is unlimited, the owner's current balance, and the net spendable amount right now.

## Facts

- Endpoint: GET https://onchaincheck.dev/polygon/allowance?utm_source=zero.xyz
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/polygon-pos-erc-20-allowance-checker-3155fc65
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Hex3L4l1Nwnmr_EURlRrr

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 polygon-pos-erc-20-allowance-checker-3155fc65
```

Example prompt: What's the USDC allowance on Polygon PoS for spender 0x429eba38eF16A42C62b497C22A4662C45b37f848 from owner 0x357542d88744DB4BFfE8F90008138dDc4a10cdC3 — is it unlimited, and how much can the spender actually move right now?

## When to prefer this

Use this endpoint when you need to check ERC-20 token approvals specifically on Polygon PoS, including whether an approval is effectively unlimited (max uint256). Prefer this over generic block explorers when you need a structured, machine-readable response combining allowance, balance, and spendable amount in one call. Ideal for DeFi security checks, approval audits, and pre-transaction validation on Polygon.

## Known failure modes

- Invalid Ethereum address format returns a validation error
- Token contract address is not a valid ERC-20 on Polygon PoS — returns error or zero values
- Owner or spender address does not exist onchain — returns zero allowance and balance
- Network connectivity issues to Polygon PoS RPC — may return 5xx error
- Payment not included or invalid — returns 402 Payment Required

## How this service works

ERC-20 allowance on Polygon PoS: how much a spender may transfer from an owner, whether the approval is effectively unlimited, the owner's balance, and the amount the spender could move right now.

## Output

A JSON object containing the raw and human-readable allowance, whether it is effectively unlimited (boolean), the owner's current ERC-20 balance, the net amount the spender can move right now (minimum of allowance and balance), the token symbol, and the chain identifier.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "token",
      "owner",
      "spender"
     ],
     "properties": {
      "owner": {
       "type": "string",
       "pattern": "^0x[0-9a-fA-F]{40}$",
       "description": "Address that granted the approval"
      },
      "token": {
       "type": "string",
       "pattern": "^0x[0-9a-fA-F]{40}$",
       "description": "ERC-20 contract on Polygon PoS"
      },
      "spender": {
       "type": "string",
       "pattern": "^0x[0-9a-fA-F]{40}$",
       "description": "Address allowed to spend"
      }
     },
     "additionalProperties": false
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "raw": "115792089237316195423570985008687907853269984665640564039457584007913129639935",
  "chain": "polygon",
  "owner": "0x357542d88744DB4BFfE8F90008138dDc4a10cdC3",
  "token": "0x3c499c542cEF5E3811e1192ce70d8cC03d5c3359",
  "symbol": "USDC",
  "spender": "0x429eba38eF16A42C62b497C22A4662C45b37f848",
  "allowance": "115792089237316195423570985008687907853269984665640564039457584007913129.639935",
  "unlimited": true,
  "ownerBalance": "0",
  "spendableNow": "0"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/polygon-pos-erc-20-allowance-checker-3155fc65/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from onchaincheck.dev](https://www.zero.xyz/host/onchaincheck.dev/llms.txt)