Diagnose cron expressions and catch silent scheduling failures

cron-doctor is one of the free skills in takeaseat's devops-skills collection, a set of self-contained Claude Code agent skills built for the tedious, error-prone parts of infrastructure and scheduling work. It diagnoses cron expressions for the class of "silent failures" that pass every check but never actually run correctly: impossible schedules (the classic case being a syntactically valid expression like 0 0 30 2 * that never fires because February never has a 30th day), OR-semantics traps, midnight spikes, and schedule drift. Under the hood it runs on cron-doctor/scripts/cron-engine.js, a 638-line, zero-dependency engine backed by 69 passing tests - the same engine that separately powers takeaseat's "Cron Helper" VS Code extension and its hosted cron validation API.

Use it when you want an agent to catch a broken or misleading cron schedule before it ships - an impossible date, a misread OR-semantics rule, an accidental midnight pile-up, or drift between what a schedule says and what it actually does. It is one of two free skills in the devops-skills collection, alongside env-drift-hunter (which finds env-var drift across .env files before deploy). It does not audit Dockerfiles, diagnose CI/CD pipeline failures, lint Kubernetes manifests, or scan for leaked secrets - those four capabilities exist in the same repository but are gated behind a separate Pro license and are not part of cron-doctor. The devops-skills collection frames this whole class of problem as "silent failures" - config that passes every check until it doesn't - and cron-doctor is the skill built specifically to catch that failure mode in scheduling before it ships.

As an Agent Skills-spec skill, cron-doctor ships as a self-contained folder: a SKILL.md with YAML frontmatter plus its zero-dependency scripts/cron-engine.js and any reference docs the agent loads on demand. It carries no telemetry and no runtime dependencies of its own.

Install by cloning the devops-skills repo and copying the skill folder into ~/.claude/skills/ (git clone https://github.com/takeaseatventure/devops-skills.git then cp -r devops-skills/skills/* ~/.claude/skills/), or through Claude Code's plugin system via the repo's skills.sh one-click installer. The same cron-engine.js also powers two separate takeaseat products outside Claude Code: the "Cron Helper" VS Code extension and a hosted cron validation API.

Anyone running Claude Code, or another AI coding agent that supports the Agent Skills spec, who wants scheduling bugs caught before they reach production rather than discovered at 3am. cron-doctor itself is MIT licensed and free; the other skills in the same collection require an $8/mo All-Access Pro license. It is built by takeaseat, whose stated pitch for the whole collection is "your config, made legible."