# Mach Gallery Base ERC-20 Allowance Lookup

> Mach Gallery Base ERC-20 Allowance Lookup is a paid API for AI agents from api.mach.gallery, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-02).

Returns the ERC-20 token allowance granted by an owner to a spender on the Base network

## Facts

- Endpoint: POST https://api.mach.gallery/api/base/allowance?utm_source=zero.xyz
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/mach-gallery-base-erc-20-allowance-lookup-cadacf81
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_a16m003xUF6Ju1SfYyYX0

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 mach-gallery-base-erc-20-allowance-lookup-cadacf81 -d '<json body>'
```

Example prompt: Check the USDC allowance that my wallet 0xAbC1234567890abcdef1234567890ABCDEF12345 has approved for the Uniswap router 0xDef9876543210DEFabc9876543210DEFabc98765 on Base — what's the current token approval amount?

## When to prefer this

Choose this endpoint when you need a fast, pay-per-call allowance check on the Base network without managing API keys or subscriptions. It is ideal for autonomous agents that need on-demand ERC-20 approval data at low cost ($0.003/call) and can pay via USDC over x402. Prefer it over building your own RPC calls when simplicity and cost predictability matter.

## Known failure modes

- Invalid EVM address format for owner, token, or spender returns a validation error
- Token address does not correspond to a deployed ERC-20 contract on Base, resulting in an error or zero allowance
- Network congestion or RPC node issues may cause timeouts
- Payment failure via x402 if insufficient USDC balance prevents the $0.003 call fee

## How this service works

Fast, low-cost Base data for autonomous agents. No API keys, no subscriptions; pay per call with USDC over x402.

## Output

Returns a JSON object containing the network identifier (e.g. 'eip155:8453' for Base mainnet) and the allowance amount in atomic units (smallest denomination) as a string, representing how many tokens the spender is authorized to transfer on behalf of the owner.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "owner": {
   "type": "string",
   "pattern": "^0x[0-9a-fA-F]{40}$",
   "description": "ERC-20 token owner address on Base mainnet."
  },
  "token": {
   "type": "string",
   "pattern": "^0x[0-9a-fA-F]{40}$",
   "description": "ERC-20 or token contract address on Base mainnet."
  },
  "spender": {
   "type": "string",
   "pattern": "^0x[0-9a-fA-F]{40}$",
   "description": "ERC-20 spender address whose allowance is being checked."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "network": "eip155:8453",
  "allowance_atomic": "0"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/mach-gallery-base-erc-20-allowance-lookup-cadacf81/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.mach.gallery](https://www.zero.xyz/host/api.mach.gallery/llms.txt)