CronSpell

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Validate and explain cron expressions; list next/previous run times in any time zone, DST-aware.

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cron_runs_between Read-only

List every run of a cron expression between start and end (both inclusive) in an IANA time zone, DST-aware, oldest first. Default limit 20, max 100; truncated is true when there are more. Read-only. Same engine as GET /api/between.

endstring, required

Window end (inclusive). ISO 8601 with Z or an offset (2026-11-01T09:00:00Z), a local time read in the time zone (2026-11-01T09:00), or unix seconds.

startstring, required

Window start (inclusive). ISO 8601 with Z or an offset (2026-11-01T09:00:00Z), a local time read in the time zone (2026-11-01T09:00), or unix seconds.

expressionstring, required

Cron expression, e.g. "0 9 * * 1-5", "*/15 * * * *", "0 30 8 * * *" (6 fields = leading seconds) or "@daily".

limitinteger

Max runs to return (1-100).

timezonestring

IANA time zone the schedule runs in, e.g. "America/Denver", "Europe/London". Default UTC.

Tools (4)

cron_runs_between

read-only

Argument	Type	Description
end*	string	Window end (inclusive). ISO 8601 with Z or an offset (2026-11-01T09:00:00Z), a local time read in the time zone (2026-11-01T09:00), or unix seconds.
limit	integer	Max runs to return (1-100).
start*	string	Window start (inclusive). ISO 8601 with Z or an offset (2026-11-01T09:00:00Z), a local time read in the time zone (2026-11-01T09:00), or unix seconds.
timezone	string	IANA time zone the schedule runs in, e.g. "America/Denver", "Europe/London". Default UTC.
expression*	string	Cron expression, e.g. "0 9 * * 1-5", "/15 * * ", "0 30 8 * *" (6 fields = leading seconds) or "@daily".

Input schema (JSON)

{
  "type": "object",
  "required": [
    "expression",
    "start",
    "end"
  ],
  "properties": {
    "end": {
      "type": "string",
      "maxLength": 40,
      "minLength": 1,
      "description": "Window end (inclusive). ISO 8601 with Z or an offset (2026-11-01T09:00:00Z), a local time read in the time zone (2026-11-01T09:00), or unix seconds."
    },
    "limit": {
      "type": "integer",
      "default": 20,
      "maximum": 100,
      "minimum": 1,
      "description": "Max runs to return (1-100)."
    },
    "start": {
      "type": "string",
      "maxLength": 40,
      "minLength": 1,
      "description": "Window start (inclusive). ISO 8601 with Z or an offset (2026-11-01T09:00:00Z), a local time read in the time zone (2026-11-01T09:00), or unix seconds."
    },
    "timezone": {
      "type": "string",
      "default": "UTC",
      "pattern": "^[A-Za-z0-9_+\\-/]+$",
      "maxLength": 64,
      "minLength": 1,
      "description": "IANA time zone the schedule runs in, e.g. \"America/Denver\", \"Europe/London\". Default UTC."
    },
    "expression": {
      "type": "string",
      "maxLength": 200,
      "minLength": 1,
      "description": "Cron expression, e.g. \"0 9 * * 1-5\", \"*/15 * * * *\", \"0 30 8 * * *\" (6 fields = leading seconds) or \"@daily\"."
    }
  },
  "additionalProperties": false
}

explain_cron

Explain a cron expression in plain English, e.g. "0 9 * * 1-5" → "At 09:00, on Monday through Friday." Also returns notes on cron rules that often surprise people (day-of-month OR day-of-week, seconds field, shorthand expansion). Invalid expressions return isError with the reason. Read-only. Same engine as GET /api/explain.

read-only

Argument	Type	Description
expression*	string	Cron expression, e.g. "0 9 * * 1-5", "/15 * * ", "0 30 8 * *" (6 fields = leading seconds) or "@daily".

Input schema (JSON)

{
  "type": "object",
  "required": [
    "expression"
  ],
  "properties": {
    "expression": {
      "type": "string",
      "maxLength": 200,
      "minLength": 1,
      "description": "Cron expression, e.g. \"0 9 * * 1-5\", \"*/15 * * * *\", \"0 30 8 * * *\" (6 fields = leading seconds) or \"@daily\"."
    }
  },
  "additionalProperties": false
}

next_cron_runs

List the next (or, with direction "previous", the most recent past) run times of a cron expression in an IANA time zone, DST-aware. Each run has the local time with its UTC offset, the UTC time, unix seconds and weekday. Default 5 runs, max 20; searches up to 50 years. Read-only. Same engine as GET /api/next and GET /api/previous.

read-only

Argument	Type	Description
from	string	Start point (exclusive); default now. ISO 8601 with Z or an offset (2026-11-01T09:00:00Z), a local time read in the time zone (2026-11-01T09:00), or unix seconds.
count	integer	How many runs (1-20).
timezone	string	IANA time zone the schedule runs in, e.g. "America/Denver", "Europe/London". Default UTC.
direction	string	"next" (default) or "previous" (most recent first).
expression*	string	Cron expression, e.g. "0 9 * * 1-5", "/15 * * ", "0 30 8 * *" (6 fields = leading seconds) or "@daily".

Input schema (JSON)

{
  "type": "object",
  "required": [
    "expression"
  ],
  "properties": {
    "from": {
      "type": "string",
      "maxLength": 40,
      "description": "Start point (exclusive); default now. ISO 8601 with Z or an offset (2026-11-01T09:00:00Z), a local time read in the time zone (2026-11-01T09:00), or unix seconds."
    },
    "count": {
      "type": "integer",
      "default": 5,
      "maximum": 20,
      "minimum": 1,
      "description": "How many runs (1-20)."
    },
    "timezone": {
      "type": "string",
      "default": "UTC",
      "pattern": "^[A-Za-z0-9_+\\-/]+$",
      "maxLength": 64,
      "minLength": 1,
      "description": "IANA time zone the schedule runs in, e.g. \"America/Denver\", \"Europe/London\". Default UTC."
    },
    "direction": {
      "enum": [
        "next",
        "previous"
      ],
      "type": "string",
      "default": "next",
      "description": "\"next\" (default) or \"previous\" (most recent first)."
    },
    "expression": {
      "type": "string",
      "maxLength": 200,
      "minLength": 1,
      "description": "Cron expression, e.g. \"0 9 * * 1-5\", \"*/15 * * * *\", \"0 30 8 * * *\" (6 fields = leading seconds) or \"@daily\"."
    }
  },
  "additionalProperties": false
}

validate_cron

Check whether a cron expression is valid. Returns valid true with the expanded values of every field (minute, hour, day of month, month, day of week, and seconds for 6-field expressions), or valid false with an error code, the field at fault and a message. Detects schedules that can never run (e.g. February 30). Read-only. Same engine as GET /api/validate.

read-only

Argument	Type	Description
expression*	string	Cron expression, e.g. "0 9 * * 1-5", "/15 * * ", "0 30 8 * *" (6 fields = leading seconds) or "@daily".

Input schema (JSON)

{
  "type": "object",
  "required": [
    "expression"
  ],
  "properties": {
    "expression": {
      "type": "string",
      "maxLength": 200,
      "minLength": 1,
      "description": "Cron expression, e.g. \"0 9 * * 1-5\", \"*/15 * * * *\", \"0 30 8 * * *\" (6 fields = leading seconds) or \"@daily\"."
    }
  },
  "additionalProperties": false
}