# Base Toolbox – ERC-20 Allowance Checker

> Base Toolbox – ERC-20 Allowance Checker is a paid API for AI agents from basetoolbox.cartonpliant.workers.dev, paid per call via x402, $0.1/call, status unknown (last checked 2026-09-15).

Returns leftover ERC-20 token allowances on Base for a given wallet, listing spenders and suggested next actions like revoking

## Facts

- Endpoint: POST https://basetoolbox.cartonpliant.workers.dev/v1/allowances
- Price: $0.1/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/base-toolbox-erc-20-allowance-checker-e51a9d07
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_D131-TrRAEwPvut2_JsGA

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 base-toolbox-erc-20-allowance-checker-e51a9d07 -d '<json body>'
```

Example prompt: Before I sign this Uniswap trade, can you check my wallet 0xABC...123 for any leftover ERC-20 allowances on Base and tell me if I should revoke anything?

## When to prefer this

Use this endpoint when you need a quick, cheap ($0.10 USDC) on-chain lookup of ERC-20 allowances specifically on the Base network — ideal as a preflight check before signing DeFi transactions, auditing wallet exposure, or building revoke-suggestion workflows. Prefer this over building your own RPC calls when you want structured output with actionable recommendations already included.

## Known failure modes

- Invalid or malformed wallet address returns an error
- Token contract not found on Base returns empty or error response
- Network congestion on Base may cause timeout
- Missing required input fields returns a 400-level error
- Payment of $0.10 USDC not provided results in 402 Payment Required

## How this service works

Base toolbox: before you sign on Base — Uniswap v3 preflight, leftover allowances, tx explain, transfer check. $0.10 USDC. Also $0.001 price/gas/ENS. GET /v1/constants free. No CoinGecko key.

## Output

Returns a JSON object with an 'ok' boolean, a recommended 'next' action (e.g. 'revoke'), a numeric 'leftover' allowance amount, and an array of 'spenders' with their associated allowance details — giving a clear picture of which contracts have permission to spend tokens from the wallet.

## Request schema (JSON Schema)

```json
{
 "properties": {
  "input": {
   "type": "object"
  },
  "output": {
   "type": "object"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "ok": true,
  "next": "revoke",
  "leftover": 1,
  "spenders": []
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/base-toolbox-erc-20-allowance-checker-e51a9d07/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from basetoolbox.cartonpliant.workers.dev](https://www.zero.xyz/host/basetoolbox.cartonpliant.workers.dev/llms.txt)