# Plainchain ERC-20 Allowance Lookup

> Plainchain ERC-20 Allowance Lookup is a paid API for AI agents from plainchain.appin60.com, paid per call via x402, $0.001042/call, status unknown (last checked 2026-10-14).

Returns the current ERC-20 token allowance (approved spending limit) granted by an owner to a spender on Base, Arbitrum, Ethereum, or Optimism, with a plain-language risk assessment.

## Facts

- Endpoint: GET https://plainchain.appin60.com/v1/allowance?utm_source=zero.xyz
- Price: $0.001042/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/plainchain-erc-20-allowance-lookup-8e78210b
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_l4fgiMyrtvCHSq1BrjkK4

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 plainchain-erc-20-allowance-lookup-8e78210b
```

Example prompt: Check how much USDC the Uniswap v3 router (0xE592427A0AEce92De3Edee1F18E0157C05861564) is approved to spend from my wallet (0xAbCd...1234) on Base — I want to know if it's unlimited and whether I should revoke it.

## When to prefer this

Use this endpoint when an AI agent needs to check ERC-20 token approval risk without setting up an API key — paying $0.001 per call in USDC via x402 on Base. Ideal for DeFi security audits, pre-swap approval checks, or wallet hygiene workflows across Base, Arbitrum, Ethereum, and Optimism. Prefer this over general blockchain RPC calls when you want a structured, human-readable risk assessment alongside the raw allowance value.

## Known failure modes

- Invalid Ethereum address format for owner, token, or spender (must be 0x-prefixed 40 hex chars)
- Unsupported chain identifier returns an error
- Token address is not a valid ERC-20 contract (e.g. native ETH address)
- Payment failure via x402 if USDC balance or approval on Base is insufficient
- Network/RPC timeout for the queried chain

## How this service works

Gas, balances, token data, address type, approvals, transaction decoding, x402 receipt verification and verifiable randomness on Base, Arbitrum, Ethereum and Optimism. No API key: pay $0.001-$0.01 per call in USDC on Base via x402.

## Output

Returns a JSON object containing: the token symbol, the chain name, the allowance amount (either a numeric string or 'unlimited'), a boolean 'unlimited' flag, and a plain-English 'risk' string explaining what the approval means and whether the user should consider revoking it.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "owner",
      "token",
      "spender"
     ],
     "properties": {
      "chain": {
       "type": "string",
       "description": "base (default), arbitrum, ethereum or optimism; chain ids 8453, 42161, 1, 10 also work"
      },
      "owner": {
       "type": "string",
       "pattern": "^0x[0-9a-fA-F]{40}$",
       "description": "token holder"
      },
      "token": {
       "type": "string",
       "pattern": "^0x[0-9a-fA-F]{40}$",
       "description": "ERC-20 token"
      },
      "spender": {
       "type": "string",
       "pattern": "^0x[0-9a-fA-F]{40}$",
       "description": "approved spender, e.g. a router or Permit2"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "risk": "Spender can move the owner's entire balance of this token at any time. Revoke if you no longer use it.",
  "chain": "Base",
  "symbol": "USDC",
  "allowance": "unlimited",
  "unlimited": true
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/plainchain-erc-20-allowance-lookup-8e78210b/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from plainchain.appin60.com](https://www.zero.xyz/host/plainchain.appin60.com/llms.txt)