Paste any cron expression and get a plain-English explanation instantly. Supports standard 5-field and extended 6-field syntax, plus shorthand keywords like @hourly. Free API for AI agents and developers.
A cron expression is a string of five (or six) fields separated by spaces that defines a recurring schedule. Originally from Unix crontab, this syntax is now used everywhere: CI/CD pipelines, cloud schedulers, Kubernetes CronJobs, and agent heartbeat intervals. Each field constrains when the job runs.
Send a POST request with the cron expression. The API returns the plain-English explanation, next run times, and field breakdown.
curl -X POST https://api.delx.ai/api/v1/utils/cron-explain \
-H "Content-Type: application/json" \
-d '{"expression": "*/5 * * * *"}'
# Response:
# {
# "expression": "*/5 * * * *",
# "explanation": "Every 5 minutes",
# "fields": {
# "minute": "*/5 (every 5th minute)",
# "hour": "* (every hour)",
# "day_of_month": "* (every day)",
# "month": "* (every month)",
# "day_of_week": "* (every weekday)"
# },
# "next_runs": [
# "2026-03-14T12:05:00Z",
# "2026-03-14T12:10:00Z",
# "2026-03-14T12:15:00Z"
# ]
# }| Expression | Schedule |
|---|---|
| */5 * * * * | Every 5 minutes |
| 0 * * * * | Every hour (at minute 0) |
| 0 0 * * * | Daily at midnight UTC |
| 0 9 * * 1-5 | Weekdays at 9:00 AM UTC |
| 0 0 * * 0 | Weekly on Sunday at midnight |
| 0 0 1 * * | Monthly on the 1st at midnight |
| */30 * * * * | Every 30 minutes |
| Position | Field | Allowed Values |
|---|---|---|
| 1 | Minute | 0-59 |
| 2 | Hour | 0-23 |
| 3 | Day of month | 1-31 |
| 4 | Month | 1-12 (or JAN-DEC) |
| 5 | Day of week | 0-7 (0 and 7 = Sunday, or SUN-SAT) |
| Character | Meaning | Example |
|---|---|---|
| * | Any value | * in hour = every hour |
| / | Step interval | */15 = every 15 units |
| - | Range | 1-5 = Monday to Friday |
| , | List | 1,15 = 1st and 15th |
AI agents use cron expressions to schedule recurring tasks: heartbeat pings, data pipeline runs, report generation, and health checks. Following OpenClaw best practices, agents should validate their cron schedules before registration. A misconfigured expression (e.g. * * * * * running every minute instead of every hour) can cause rate-limit bans or excessive resource usage.
# Validate before deploying a heartbeat schedule
curl -X POST https://api.delx.ai/api/v1/utils/cron-explain \
-H "Content-Type: application/json" \
-d '{"expression": "*/3 * * * *"}'
# => "Every 3 minutes" — good for fast_monitor
# => next_runs shows the exact upcoming trigger timesStandard (5-field) cron uses: minute, hour, day-of-month, month, day-of-week. Extended (6-field) cron adds a leading seconds field. This explainer auto-detects which format you are using based on the number of fields.
Yes. If the expression is invalid, the API returns a clear error message explaining which field is wrong and what values are allowed. This makes it useful as both a validator and an explainer.
Yes. The explainer recognizes shorthand keywords including @yearly, @annually, @monthly, @weekly, @daily, @midnight, @hourly, and @reboot. Each is expanded to its equivalent 5-field expression in the response.