ToolVet
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Token Allowance

by ERC-20 Token Allowance API in Onchain & crypto

x402 APIPassing, checked 11 min ago

Live ERC-20 spending allowance an owner has granted a spender: calls `allowance(owner, spender)` on the token and returns the raw amount, a decimal-formatted amount (using the token's decimals) with its symbol, and an `isUnlimited` flag for effectively-infinite approvals. Use it to audit token approvals / approval risk before signing. Reads live on-chain data with automatic endpoint fallback.

POST
https://chain.openverbs.com/v1/token-allowance
Price
$0.002
per call in USDC
Uptime
100%
last 30 days
Response time
533 ms
624 ms slowest 5%
Last check
Passed
11 min ago, next in 21 min

Run a free test callHow to call it

Reliability

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Status and outage history · Atom feed · Watch with other listings

How to call it

POST https://chain.openverbs.com/v1/token-allowance

Each call costs $0.002 in USDC on Base, paid with the request over x402.

Run a free test callOne unpaid request, the way an agent sends it. You see the payment challenge it gets back. Nothing is charged.

Example request

From the listing.

POST https://chain.openverbs.com/v1/token-allowance
content-type: application/json

{
  "chain": "base",
  "owner": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
  "spender": "0x0000000000000000000000000000000000000001",
  "token": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"
}

Parameters

ParameterTypeRequiredDescription
chainstringNoEVM chain to query. One of: ethereum, base, arbitrum, optimism, polygon. Default "ethereum". One of: ethereum, base, arbitrum, optimism, polygon.
ownerstringYesToken holder that granted the approval.
spenderstringYesApproved spender address.
tokenstringYesERC-20 token contract address.

Example response

The listing has no example response.

Call it from code

The curl command shows the payment challenge. The JavaScript and Python versions pay and call, and never pay more than $0.002.

curl: see the payment challenge
# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i -X POST 'https://chain.openverbs.com/v1/token-allowance' \
  -H 'content-type: application/json' \
  --data-raw '{"chain":"base","owner":"0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045","spender":"0x0000000000000000000000000000000000000001","token":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"}'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - -X POST 'https://chain.openverbs.com/v1/token-allowance' \
  -H 'content-type: application/json' \
  --data-raw '{"chain":"base","owner":"0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045","spender":"0x0000000000000000000000000000000000000001","token":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"}' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode
JavaScript: pay and call
// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.002 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.002" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.002 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fchain.openverbs.com%2Fv1%2Ftoken-allowance&method=POST
const res = await pay("https://chain.openverbs.com/v1/token-allowance", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({
    "chain": "base",
    "owner": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
    "spender": "0x0000000000000000000000000000000000000001",
    "token": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"
  }),
});
console.log(res.status, await res.text());
Python: pay and call
# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.002 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.002"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.post(
        "https://chain.openverbs.com/v1/token-allowance",
        json={
            "chain": "base",
            "owner": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
            "spender": "0x0000000000000000000000000000000000000001",
            "token": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
        },
    )
    print(res.status_code, res.text)

Security scan

No findings

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Recent checks

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