ToolVet
78trust / 100

Chain Selector

by Duo Data Utilities in Onchain & crypto

x402 APIPassing, checked 3 h ago

Compute the Keccak-256 hash of a Solidity function or event signature and derive the 4-byte function selector and the 32-byte event topic. Normalises the signature first — strips parameter names, expands uint to uint256 and the other aliases, flattens tuples — so a signature copied from source code produces the same selector as the canonical form. Also hashes arbitrary text or hex bytes with Keccak-256.

GET
https://api.duoleads.com/v1/chain/selector
Price
$0.05
per call in USDC
Uptime
100%
last 30 days
Response time
195 ms
741 ms slowest 5%
Last check
Passed
3 h ago, next any minute now

Run a free test callHow to call it

Reliability

All checks passedSome failedAll failedNot checked

Status and outage history · Atom feed

How to call it

GET https://api.duoleads.com/v1/chain/selector

Each call costs $0.05 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.

GET https://api.duoleads.com/v1/chain/selector?signature=transfer%28address%2Cuint256%29

Parameters

ParameterTypeRequiredDescription
datastringNoAlternative to signature: raw data to Keccak-256 hash.
encodingstringNoEncoding of data: utf8 (default) or hex. One of: utf8, hex. Default: "utf8".
kindstringNofunction (default), event or error. One of: function, event, error. Default: "function".
signaturestringNoSolidity function, event or error signature, e.g. transfer(address to, uint amount).

Example response

The provider's example. We can't check it without paying.

{
  "data": {
    "canonical": "transfer(address,uint256)",
    "inputs": [
      "address",
      "uint256"
    ],
    "keccak256": "0xa9059cbb2ab09eb219583f4a59a5d0623ade346d962bcd4e46b11da047c9049b",
    "normalisations": [],
    "selector": "0xa9059cbb",
    "topic0": null
  },
  "meta": {
    "computed_at": "2026-09-28T12:00:00.000Z",
    "deterministic": true,
    "disclaimer": "Factual output of a deterministic computation over public data. Provided as is, with no warranty of accuracy, completeness or availability. Not investment, financial, legal, tax, medical or any other professional advice, and not a recommendation. Verify before relying on it. Terms: https://api.duoleads.com/terms",
    "price_usd": "0.05",
    "request_id": "01K6B7Q4ZC8H3F2M9WXR5TYN0D"
  },
  "ok": true,
  "route": "/v1/chain/selector",
  "version": "1.0.0"
}

Call it from code

The curl command shows the payment challenge. The JavaScript and Python versions pay and call, and never pay more than $0.05.

curl: see the payment challenge
# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://api.duoleads.com/v1/chain/selector?signature=transfer%28address%2Cuint256%29'

# 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 - 'https://api.duoleads.com/v1/chain/selector?signature=transfer%28address%2Cuint256%29' \
  | 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 $0.05 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.05" });
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 $0.05 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fapi.duoleads.com%2Fv1%2Fchain%2Fselector
const res = await pay("https://api.duoleads.com/v1/chain/selector?signature=transfer%28address%2Cuint256%29");
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 $0.05 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.05"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://api.duoleads.com/v1/chain/selector?signature=transfer%28address%2Cuint256%29")
    print(res.status_code, res.text)

Security scan

No findings

We scan names, descriptions and tool definitions for hidden instructions and other prompt-injection patterns.

Recent checks

WhenResultHTTPTimePrice
3 h agoPassed402206 ms$0.05
8 h agoPassed402591 ms$0.05
12 h agoPassed40271 ms$0.05
16 h agoPassed402128 ms$0.05
20 h agoPassed40270 ms$0.05
Show 10 older checks
25 h agoPassed40282 ms$0.05
29 h agoPassed402605 ms$0.05
32 h agoPassed402463 ms$0.05
36 h agoPassed40238 ms$0.05
40 h agoPassed402195 ms$0.05
44 h agoPassed402135 ms$0.05
2 days agoPassed402125 ms$0.05
2 days agoPassed402499 ms$0.05
2 days agoPassed402961 ms$0.05
2 days agoPassed402135 ms$0.05