⏰Cron Explainer
Turn a cron expression into plain English, validate it, and compute the exact next execution times. Deterministic — the answer to 'when does this cron actually fire?' without guessing.
Worked examples
Weekdays at 9am
GET /api/v1/dev/cron-describe?expr=0%209%20*%20*%201-5&ref=2026-10-01T09%3A00%3A00Z
Result: At 09:00 AM, Monday through Friday
Every 15 minutes
GET /api/v1/dev/cron-describe?expr=*%2F15%20*%20*%20*%20*&ref=2026-10-01T09%3A00%3A00Z
Result: Every 15 minutes
First of month, midnight
GET /api/v1/dev/cron-describe?expr=0%200%201%20*%20*&ref=2026-10-01T09%3A00%3A00Z
Result: At 12:00 AM, on day 1 of the month
Machine API (x402)
$0.001 / callThis tool is also a JSON API for AI agents. Requests without payment receive 402 Payment Required plus instructions; agents pay USDC on Base via the x402 protocol — no accounts, no API keys.
GET /api/v1/dev/cron-describe?expr=0%209%20*%20*%201-5&ref=2026-10-01T09%3A00%3A00Z HTTP/1.1
Host: agenttools-hub.vercel.app
→ 402 (payment required, instructions in headers)
→ 200 (after X-PAYMENT header; JSON body below)
{
"tool": "dev/cron-describe",
"input": {"expr":"0 9 * * 1-5","ref":"2026-10-01T09:00:00Z"},
"result": { "value": null, "answer": "At 09:00 AM, Monday through Friday" }
}Agent docs: /llms.txt · OpenAPI spec · integration guide
About this tool
Cron expressions are write-only code. This tool reads one back at you in plain English, proves it's valid, and computes the next five exact execution times in UTC — so '0 9 * * 1-5' can never silently mean something else.
description = cronstrue(expr) · next runs = schedule iteration from reference moment
Frequently asked questions
Which cron dialect is supported?
Standard 5-field cron (minute, hour, day-of-month, month, day-of-week) with common syntax like */n, ranges and lists. Year fields and seconds are not part of the 5-field dialect.
Are the next runs in UTC?
Yes — cron expressions are timezone-less; the times shown are UTC. Convert to your local zone with the current-time tool if needed.