Cron expression explainer

Parse a standard 5-field cron expression (minute hour day-of-month month day-of-week) and return a human-readable explanation. Supports wildcards (*), ranges (1-5), lists (1,3,5), steps (*/15), and named months/days (JAN, MON). ?expression=0+9+*+*+1-5.

Input

Field	Type	Description
expression *	string	5-field cron expression (minute hour dom month dow)

Example output

{
  "expression": "0 9 * * 1-5",
  "fields": {
    "minute": "0",
    "hour": "9",
    "dayOfMonth": "*",
    "month": "*",
    "dayOfWeek": "1-5"
  },
  "summary": "At 09:00, every day, day of week Monday through Friday"
}

Try it — see the 402 challenge (free)

curl -i "https://agent402.tools/api/cron-explain?expression=0+9+*+*+1-5"

The response is HTTP 402 Payment Required with exact payment requirements. Any x402 v2 client pays automatically and retries:

Paid call (JavaScript agent)

import { wrapFetchWithPayment } from "@x402/fetch";
import { x402Client } from "@x402/core/client";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const client = new x402Client();
registerExactEvmScheme(client, { signer: privateKeyToAccount(KEY) });
const payFetch = wrapFetchWithPayment(fetch, client);

const res = await payFetch("https://agent402.tools/api/cron-explain?expression=0+9+*+*+1-5");

No wallet? Pay with compute

This is a pure-CPU tool, so an agent without a wallet can pay with proof-of-work instead of USDC: fetch a challenge, solve the sha256 puzzle (16 leading zero bits — a fraction of a second of CPU, no money, no AI tokens), and resend with the X-Pow-Solution header.

import { createHash } from "node:crypto";
const lz = (b) => { let t = 0; for (const x of b) { if (!x) { t += 8; continue; } t += Math.clz32(x) - 24; break; } return t; };
const c = await (await fetch("https://agent402.tools/api/pow/challenge?slug=cron-explain")).json();
let n = 0;
while (lz(createHash("sha256").update(c.challenge + ":" + n).digest()) < c.difficulty) n++;
await fetch("https://agent402.tools/api/cron-explain", { method: "GET", headers: { "X-Pow-Solution": c.token + ":" + n } });

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