# ERC20 Allowance Checker

> ERC20 Allowance Checker is a paid API for AI agents from flat-rate-llm.kikoribera03.workers.dev, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15).

Returns how many tokens a spender is approved to transfer on an ERC20 owner's behalf, including whether the approval is effectively unlimited.

## Facts

- Endpoint: POST https://flat-rate-llm.kikoribera03.workers.dev/v1/evm/erc20-allowance
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/erc20-allowance-checker-deb186d3
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Duw5FlO8Zg3lMrykOLmQq

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 erc20-allowance-checker-deb186d3 -d '<json body>'
```

Example prompt: Check the ERC20 allowance on Base — how many USDC tokens is the Uniswap router (0x3fC91A3afd70395Cd496C647d5a6CC9D4B2b7FAD) approved to spend from my wallet (0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045), and is the approval unlimited?

## When to prefer this

Use this endpoint when you need a quick, read-only ERC20 allowance lookup without setting up your own RPC connection or Web3 library. It is ideal for agents performing DeFi safety checks, pre-flight approval validation before a swap or transfer, or auditing wallets for forgotten infinite approvals. Prefer this over raw eth_call endpoints when you want decimals-adjusted human-readable output and the unlimited flag already computed.

## Known failure modes

- Invalid or non-checksummed Ethereum address returns an error
- Unsupported chain name returns a validation error
- Non-ERC20 contract address (e.g. EOA or non-standard contract) may return zero or error
- Network congestion or RPC errors may cause timeouts
- Token contract with no allowance function returns an error

## How this service works

60 paid endpoints with no metering, no API key and no account. Each endpoint has one flat price per call, whatever the size of the request: LLM completions with automatic failover across several large models, read-only EVM tooling over Base, Ethereum, Polygon, Arbitrum and Optimism, and pure crypto utilities that touch no network.

## Output

Returns an object with: raw (raw big-integer allowance as a string), amount (human-readable decimal amount adjusted for token decimals), decimals (the token's decimal precision), and unlimited (boolean flag indicating whether the approval is effectively infinite, i.e. max uint256).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "owner",
  "token",
  "spender"
 ],
 "properties": {
  "chain": {
   "type": "string",
   "description": "base | ethereum | polygon | arbitrum | optimism."
  },
  "owner": {
   "type": "string",
   "description": "Address that owns the tokens."
  },
  "token": {
   "type": "string",
   "description": "ERC20 contract address."
  },
  "spender": {
   "type": "string",
   "description": "Address allowed to spend them."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "raw": {
   "type": "string"
  },
  "amount": {
   "type": "number"
  },
  "decimals": {
   "type": "number"
  },
  "unlimited": {
   "type": "boolean"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/erc20-allowance-checker-deb186d3/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from flat-rate-llm.kikoribera03.workers.dev](https://www.zero.xyz/host/flat-rate-llm.kikoribera03.workers.dev/llms.txt)