Parse cron expressions, preview next N run times, and validate crontab syntax via @mukundakatta/cron-mcp (npx)

@mukundakatta/cron-mcp v0.1.0 — verified recipe

Install: npm install @mukundakatta/cron-mcp @modelcontextprotocol/sdk Entry: dist/server.js (stdio transport) Tools: 2 — next, validate

Tool 1: next({expression, n?, from?})

Compute next N firing times for a cron expression in UTC ISO 8601.

next({expression:"0 0 * * *"})                → 5 daily-midnight dates starting from now
next({expression:"*/5 * * * *"})              → 5 dates at 5-min intervals
next({expression:"0 9 * * 1-5"})              → weekday 9am dates (skips weekends correctly)
next({expression:"0 12 1 * *"})               → monthly 1st at noon
next({expression:"30 15 * * 0"})              → every Sunday 3:30pm
next({expression:"0 18 15,30 * *"})           → 15th and 30th at 6pm
next({expression:"*/15 9-17 * * 1-5"})        → every 15min during business hours, weekdays only
next({expression:"0 0 * * *", n:3})           → 3 dates (custom count)
next({expression:"0 0 * * *", n:10})          → 10 dates
next({expression:"0 0 * * *", from:"2025-01-01T00:00:00Z", n:3}) → Jan 2-4 2025 (custom start)
next({expression:"0 12 25 12 *", from:"2020-01-01T00:00:00Z", n:3}) → Christmas noon 2020/2021/2022
next({expression:"0 0 28-31 * *", n:5})       → handles month-end correctly (June has 30 days, skips 31)
next({expression:"0 0 0 * * *"})              → 6-field (seconds) supported
next({expression:"invalid cron"})             → isError: "cannot resolve alias \"inv\""

Tool 2: validate({expression})

Check if a cron expression is syntactically valid.

validate({expression:"0 0 * * *"})    → {valid: true}
validate({expression:"*/5 * * * *"})  → {valid: true}
validate({expression:"0 9 * * 1-5"})  → {valid: true}
validate({expression:"0 0 0 * * *"})  → {valid: true}  // 6-field with seconds
validate({expression:"invalid"})      → {valid:false, error:"Constraint error, got value 0 expected range 1-12"}
validate({expression:"60 * * * *"})   → {valid:false, error:"Constraint error, got value 60 expected range 0-59"}
validate({expression:""})             → {valid: true}  // ⚠️ empty string validates as true!

Key gotchas

• ⚠️ Param is `n` NOT `count` — using count is silently ignored (defaults to 5)
• ⚠️ Empty string validates as TRUE — validate({expression:""}) returns {valid:true} (questionable behavior)
• 6-field cron (with seconds) supported — "0 0 0 * * *" parses as midnight with 0 seconds
• `from` param accepts ISO 8601 — compute next runs from any arbitrary start date, including dates in the past
• Descriptive validation errors — "Constraint error, got value 60 expected range 0-59"
• Month-end handling correct — 28-31 * * skips days that don't exist in short months
• Weekend/weekday logic correct — 1-5 correctly skips Saturday and Sunday
• First call ~49ms JIT, subsequent calls 0-2ms
• All times in UTC — no timezone parameter

Execution stats

• 25 calls across 2 sessions, 24 successes + 1 correct rejection
• 100% correctness (the rejection is expected for invalid syntax)
• p50: 1ms, first call: 49ms (JIT), max: 49ms