CronSpell

dev.workers.mike-tusa.cronspellPublished by cronspell.mike-tusa.workers.devOfficial publisherv0.1.0Updated Oct 27, 2026

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

VerifiedStreamable HTTPWeb executableDeveloper Tools

Overview

AI-generated overview

Remote MCP server that validates and explains cron expressions and lists their upcoming or past run times in any IANA time zone.

What you can do
  • Validate cron expressions and get expanded field values or a specific error code and faulty field
  • Explain a cron expression in plain English, with notes on commonly surprising cron rules
  • List the next or previous run times in a chosen IANA time zone, DST-aware, with local time, UTC offset, unix seconds and weekday
  • List every run between a start and end time, oldest first, with a truncation flag
When to use it
Useful when writing or reviewing cron schedules for jobs, CI pipelines or schedulers and you want to confirm an expression is valid, understand what it means, or check exactly when it will fire across time zones and daylight-saving changes.
Requirements
Remote streamable HTTP endpoint; no packages, environment variables, headers or authentication are declared. Network access to the hosted endpoint is required.
Before you install
All four tools are described as read-only, so no data is changed. Expressions and time zones you submit are sent to the third-party hosted service; avoid including sensitive details in any surrounding context you share.

Installation

In SourceWeft

  1. Open CronSpell in the dashboard and add it to a workspace.
  2. Enable the server for the chats that should use its tools.

Web executable via Streamable HTTP. Remote servers run from the web runtime once configured in a workspace.

Use with an agent

Paste this prompt into Claude Code, Codex, Cursor or another agent — or into SourceWeft chat. The agent reads this server's install guide, shows you its publisher, endpoint and sign-in, and adds it to your client once you agree. Keys never go into a command.

Read https://sourceweft.com/mcp/dev.workers.mike-tusa.cronspell%2Fcronspell/install.md and connect the MCP server it describes to my client. Before changing any config, show me its publisher, endpoint and sign-in method and wait for my OK. Never put an API key in a command or in a file I would commit; ask me where it should come from.

Read the install guide the agent follows

Other MCP clients

Add this to your client's mcpServers config.

{
  "mcpServers": {
    "cronspell": {
      "type": "http",
      "url": "https://cronspell.mike-tusa.workers.dev/mcp"
    }
  }
}

Tools

4

validate_cron

Validate a cron expression

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.

Parametersexpressionrequired

explain_cron

Explain a cron expression

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.

Parametersexpressionrequired

next_cron_runs

List next (or previous) cron run times

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.

Parametersfromcounttimezonedirectionexpressionrequired

cron_runs_between

List cron runs between two times

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.

Parametersendrequiredlimitstartrequiredtimezoneexpressionrequired

Version history

1
  1. v0.1.0LatestOct 22, 2026

Score

83% of the applicable checks met

How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.

  • Reached in the last 30 daysRequired25 pts
  • Auth declaredRequired10 pts
  • Tools listedRequired15 pts
  • DescriptionRequired15 pts
  • Logo10 pts
  • Documentation15 pts

    Declare a GitHub repository with a README, or serve resource_documentation in the OAuth protected-resource metadata.

  • LicenseNot applicable

    A hosted service is used under its provider's terms, so no license is expected here. This check is left out of the percentage.