# ETH Mainnet ERC-20 Allowance

> ETH Mainnet ERC-20 Allowance is a paid API for AI agents from ari001.tailb4ac3a.ts.net, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-11).

Reads the on-chain ERC-20 token allowance on Ethereum mainnet for a given token, owner, and spender address triple.

## Facts

- Endpoint: GET https://ari001.tailb4ac3a.ts.net/v1/ventures/x402_eth_reads_v1/eth_mainnet_erc20_allowance?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-11
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/eth-mainnet-erc-20-allowance-00590ab7
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_iKoSAQYyOdAbYhzIO-dwM

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 eth-mainnet-erc-20-allowance-00590ab7
```

Example prompt: What's the current ERC-20 allowance for USDC (0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48) from my wallet 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045 to the Uniswap v3 router at 0xE592427A0AEce92De3Edee1F18E0157C05861564 on Ethereum mainnet?

## When to prefer this

Use this endpoint when you need the ERC-20 allowance specifically on Ethereum mainnet (not Base, Gnosis, or other chains). A sibling endpoint covers Base. Prefer this over generic RPC calls when you want a clean REST interface without manually encoding eth_call ABI data. Ideal for pre-transaction approval checks, wallet audits, and DeFi risk monitoring on mainnet.

## Known failure modes

- Invalid or malformed Ethereum address (not 0x + 40 hex) returns a 400 validation error
- Token address is not a deployed ERC-20 contract — call may revert or return zero
- Network connectivity issues with the Ethereum node result in a 5xx error
- Rate limiting or payment failure at $0.002 per call may cause request rejection
- Allowance may be stale if read during a pending state-change transaction

## How this service works

Ethereum mainnet ERC-20 allowance. Takes query parameters token (ERC-20 contract, 0x + 40 hex), owner (0x + 40 hex) and spender (0x + 40 hex). Returns the raw allowance read from the contract.

## Output

Returns the raw uint256 allowance value representing the maximum number of token units the spender is permitted to transfer on behalf of the owner, as currently recorded in the ERC-20 contract's storage on Ethereum mainnet.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "owner": {
       "type": "string",
       "pattern": "^0x[0-9a-fA-F]{40}$",
       "description": "0x + 40 hex"
      },
      "token": {
       "type": "string",
       "pattern": "^0x[0-9a-fA-F]{40}$",
       "description": "ERC-20 contract, 0x + 40 hex"
      },
      "spender": {
       "type": "string",
       "pattern": "^0x[0-9a-fA-F]{40}$",
       "description": "0x + 40 hex"
      }
     }
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/eth-mainnet-erc-20-allowance-00590ab7/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from ari001.tailb4ac3a.ts.net](https://www.zero.xyz/host/ari001.tailb4ac3a.ts.net/llms.txt)