# ERC-20 Allowance Checker on Base

> ERC-20 Allowance Checker on Base is a paid API for AI agents from kr-x402-mvp.kgy5612.workers.dev, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-31).

Checks how much of an ERC-20 token a spender is approved to move from an owner's wallet on Base, with risk classification, exposure calculation, and ready-to-use revoke calldata.

## Facts

- Endpoint: GET https://kr-x402-mvp.kgy5612.workers.dev/crypto/allowance?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-31
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/erc-20-allowance-checker-on-base-4639a151
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ns6zgg95K0_iCJQDAbzY3

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-on-base-4639a151
```

Example prompt: Before I do this swap, check how much USDC spender 0x000000000022D473030F116dDEE9F6B43aC78BA3 is approved to move from my wallet 0xe4be4d0bd82d8e68203deff81f79ede0529f2617 on Base, and tell me if it's risky or if I should revoke it.

## When to prefer this

Use this endpoint when your agent needs to verify ERC-20 token approvals on Base before executing swaps or transfers, or when auditing a wallet for dangerous unlimited approvals. It is purpose-built for Base with labeled spender recognition (Permit2, Uniswap, 1inch, 0x, Odos, Aerodrome) and includes pre-computed revoke calldata, making it faster than calling the blockchain directly. Prefer it over generic RPC calls when you need risk classification, exposure analysis, and actionable remediation in a single call.

## Known failure modes

- Invalid owner or spender address format (not a 0x hex address) returns 400 error
- Unknown or non-ERC-20 token address may return error or zero values
- RPC timeout or Base node unavailability causes 503 or delayed response
- Missing required owner or spender parameters returns 400
- Amount parameter as non-numeric value causes validation error
- Payment not sent or insufficient USDC balance returns 402

## How this service works

ERC-20 approval check on Base: how much can spender move from owner? owner=0x..&spender=0x..[&token=0x.., default USDC][&amount=] -> allowance, unlimited flag, owner balance, exposure (min of allowance and balance), known spender label (Permit2, Uniswap, 1inch, 0x, Odos, Aerodrome), risk class, revoke_recommended + ready approve(spender,0) calldata, can_spend when amount= given. Use before transferFrom/swap, or to audit a wallet's dangerous approvals.

## Output

A JSON object containing: current allowance (raw and human-readable), whether it is unlimited, owner's token balance, the effective exposure (min of allowance and balance), the known label for the spender (e.g. Uniswap Permit2, 1inch, Odos), a risk class (none/low/medium/high), whether revocation is recommended, ready-to-use approve(spender,0) calldata for revocation, can_spend boolean when amount is provided, and the block number at which the data was fetched.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "owner",
      "spender"
     ],
     "properties": {
      "owner": {
       "type": "string",
       "pattern": "^0x[0-9a-fA-F]{40}$",
       "examples": [
        "0xe4be4d0bd82d8e68203deff81f79ede0529f2617"
       ],
       "description": "Token holder (alias wallet)"
      },
      "token": {
       "type": "string",
       "pattern": "^0x[0-9a-fA-F]{40}$",
       "examples": [
        "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"
       ],
       "description": "Base ERC-20 (default USDC)"
      },
      "amount": {
       "type": "number",
       "examples": [
        1
       ],
       "description": "Optional amount to test can_spend"
      },
      "spender": {
       "type": "string",
       "pattern": "^0x[0-9a-fA-F]{40}$",
       "examples": [
        "0x000000000022D473030F116dDEE9F6B43aC78BA3"
       ],
       "description": "Approved spender / router"
      }
     },
     "additionalProperties": false
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "risk": "none",
  "block": 53250000,
  "chain": "base",
  "owner": "0xe4be4d0bd82d8e68203deff81f79ede0529f2617",
  "token": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
  "symbol": "USDC",
  "spender": "0x000000000022D473030F116dDEE9F6B43aC78BA3",
  "decimals": 6,
  "exposure": 0,
  "allowance": 0,
  "revoke_tx": null,
  "unlimited": false,
  "allowance_raw": "0",
  "owner_balance": 0.079,
  "spender_label": "Uniswap Permit2",
  "revoke_recommended": false
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/erc-20-allowance-checker-on-base-4639a151/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from kr-x402-mvp.kgy5612.workers.dev](https://www.zero.xyz/host/kr-x402-mvp.kgy5612.workers.dev/llms.txt)