cron-mcp
An MCP (Model Context Protocol) server that lets AI coding agents — Claude, Cursor, Copilot, Cline — parse, validate, explain, and preview cron expressions.
Built to catch silent cron bugs (impossible schedules, OR-semantics gotchas, midnight spikes) before a job is deployed — a class of mistake that's easy to make and hard to notice until a critical job silently fails to fire.
Why
Cron expressions are deceptively tricky. Common silent failures:
0 0 30 2 * → never runs (February has no 30th). Syntactically valid, semantically dead.0 0 1,15 * 1 → fires on the 1st OR 15th OR Monday, not "the 1st and 15th if Monday" (the classic dom+dow OR-semantics trap).*/7 * * * * → uneven step; intervals drift (:00, :07, :14, …, :56, :00 — not "every 7 minutes" cleanly).0 0 * * * → midnight spike; every job in the system competes at 00:00.
cron-mcp surfaces these as warnings, observations, and suggestions that the AI agent can act on — before you ship the schedule.
| Tool | Description |
|---|
parse_cron | Parse a cron expression → plain-English description of when it fires. Supports 5-field standard cron + L (last), W (nearest weekday), # (nth weekday), named months/days. |
validate_cron | Deep validation: impossible schedules, OR-semantics, midnight spikes, uneven steps, leap-year edges, frequency estimate (~runs/year). |
next_runs | Compute the next N fire times as ISO-8601 + relative offsets. |
cron_presets | Library of common, proven schedules (every 5 min, hourly, weekdays 9am, monthly, quarterly, …). |
Install
npm install -g cron-mcp-server
Published links
Claude Desktop
Add to ~/Library/Application Support/Claude/claude_desktop_config.json (macOS) or the equivalent on your OS:
{
"mcpServers": {
"cron": {
"command": "cron-mcp-server",
"args": []
}
}
}
Cursor
Add to .cursor/mcp.json (or ~/.cursor/mcp.json for global):
{
"mcpServers": {
"cron": {
"command": "cron-mcp-server"
}
}
}
VS Code (Copilot)
{
"mcp.servers": {
"cron": {
"type": "stdio",
"command": "cron-mcp-server"
}
}
}
Direct (no install)
Example usage
Once connected, just ask the agent in natural language:
- "Validate this cron:
0 0 30 2 *"
- "When does
*/5 * * * * next fire?"
- "Give me a cron for every weekday at 9am"
- "Is there anything risky about
0 0 1,15 * 1?"
The agent calls the tools and returns structured, actionable results.
Engine
The cron engine is battle-tested: 638 lines, zero dependencies, originally extracted from a browser-based cron generator and hardened with 69 unit tests. This MCP server is a thin tool wrapper around it.
License
MIT © takeaseatventure