# Aether Base Token Allowance Lookup

> Aether Base Token Allowance Lookup is a paid API for AI agents from aether-x402.vercel.app, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-12).

Queries the ERC-20 token spending allowance granted by an owner address to a spender address on Base mainnet.

## Facts

- Endpoint: POST https://aether-x402.vercel.app/v1/base/allowance?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-12
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/aether-base-token-allowance-lookup-26c6372f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_JfQwwc8_CJmI405_ifjmS

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 aether-base-token-allowance-lookup-26c6372f -d '<json body>'
```

Example prompt: Check what token allowance wallet 0xAbCd...1234 has approved for spender 0xDEF5...6789 on the USDC token contract 0xA0b8...eb48 on Base — I want to know if it's unlimited or has a specific cap.

## When to prefer this

Use this endpoint when you need a fast, pay-per-call lookup of ERC-20 token allowances on Base mainnet without setting up your own RPC infrastructure. It is ideal for AI agents that need to check approval state before executing DeFi operations, audit wallets for risky unlimited approvals, or verify spending permissions programmatically using USDC micropayments via the x402 protocol.

## Known failure modes

- Invalid Ethereum address format for owner, token, or spender returns a validation error
- Token contract address is not a valid ERC-20 contract on Base, resulting in a call failure or zero response
- Payment via x402/USDC fails if the calling agent lacks sufficient USDC balance on Base
- Rate limiting or service unavailability from the underlying Base RPC node
- Spender or owner address that has never interacted returns allowance of 0 (not an error, but may be misread as failure)

## How this service works

Pay-per-call Base onchain data, token risk verdicts and x402 payability audits over x402 (USDC on Base).

## Output

Returns a JSON object with three fields: 'raw' (the allowance as a raw integer string), 'formatted' (human-readable decimal amount), and 'unlimited' (boolean indicating whether the allowance is set to the maximum uint256 value, i.e. effectively unlimited).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "owner": {
   "type": "string",
   "pattern": "^0x[0-9a-fA-F]{40}$"
  },
  "token": {
   "type": "string",
   "pattern": "^0x[0-9a-fA-F]{40}$"
  },
  "spender": {
   "type": "string",
   "pattern": "^0x[0-9a-fA-F]{40}$"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "raw": "0",
  "formatted": "0",
  "unlimited": false
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/aether-base-token-allowance-lookup-26c6372f/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from aether-x402.vercel.app](https://www.zero.xyz/host/aether-x402.vercel.app/llms.txt)