# ERC-20 Allowance Checker

> ERC-20 Allowance Checker is a paid API for AI agents from bess-x402.onrender.com, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-29).

Returns how much a spender is approved to move from an owner's ERC-20 token balance, including an unlimited-approval flag, for pre-swap checks or approval audits.

## Facts

- Endpoint: GET https://bess-x402.onrender.com/v1/evm/allowance?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/erc-20-allowance-checker-c8771a93
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_2NvOf3tW2v3KuBZFtcfua

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-checker-c8771a93
```

Example prompt: Check how much USDC the Uniswap v3 router (0xE592427A0AEce92De3Edee1F18E0157C05861564) is approved to spend from my wallet 0xAbCd...1234 on Ethereum — and flag if it's an unlimited approval.

## When to prefer this

Choose this endpoint when you need a fast, on-chain lookup of ERC-20 spending approvals before executing a swap, bridging, or DeFi interaction, or when auditing a wallet for risky unlimited approvals. It supports major EVM chains (Ethereum, Base, Arbitrum, Optimism, Polygon) and accepts human-readable token symbols like USDC/USDT/DAI in addition to raw addresses.

## Known failure modes

- Invalid or non-checksummed token/owner/spender address returns an error
- Unsupported chain name returns a validation error
- Token address that is not an ERC-20 contract returns an error or zero allowance
- Network timeout or RPC node unavailability causes a failed response
- Querying a token with no deployed contract on the specified chain returns zero or error

## How this service works

How much a spender (router, Permit2, protocol) is approved to move from an owner's ERC-20 balance, with an unlimited-approval flag. Use to check approvals before a swap or to audit risky approvals.

## Output

Returns the current allowance amount (in token units), whether the approval is unlimited (max uint256), the token symbol, chain, owner, and spender addresses. Useful for determining whether a swap can proceed or whether a potentially dangerous blanket approval exists.

## 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",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "token",
      "owner",
      "spender"
     ],
     "properties": {
      "chain": {
       "type": "string",
       "description": "ethereum, base, arbitrum, optimism or polygon"
      },
      "owner": {
       "type": "string",
       "description": "Owner address"
      },
      "token": {
       "type": "string",
       "description": "Token address or USDC/USDT/DAI"
      },
      "spender": {
       "type": "string",
       "description": "Spender address"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/erc-20-allowance-checker-c8771a93/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from bess-x402.onrender.com](https://www.zero.xyz/host/bess-x402.onrender.com/llms.txt)