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BC Cron Explainer

Cron expression explainer, validator, and converter. Translates any cron expression into plain English ("0 */6 * * *" → "Every 6 hours, at minute 0"), shows the next 5 scheduled run times with exact dates, detects impossible/conflicting expressions (Feb 30, conflicting day-of-week + day-of-month), identifies suspicious patterns (every minute in production, very-frequent schedules on expensive operations), and converts plain English descriptions to cron ("every weekday at 9am" → "0 9 * * 1-5"). Supports all major flavors: standard Unix 5-field, 6-field with seconds, AWS EventBridge, GitHub Actions schedule, Kubernetes CronJob, Spring @Scheduled, and special strings (@yearly, @monthly, @daily, @hourly, @reboot). Also scans .github/workflows/ and Kubernetes YAML files for cron schedules and audits them. Zero external API — pure local parsing. Triggers on "cron expression", "what does this cron mean", "cron to English", "cron schedule", "explain cron", "@reboot", "/cron".

ClawHub Agent Skills author: Lucius Pang v1.0.3 MIT-0 2 files body ≈ 6 739 tokens Open the sourceclawhub.ai↗ analyzed 3 d ago

As a process C 53/100 · Has gaps — weak spots: result and completion, inputs and preconditions, failures and branches

AnalyzerKubernetesGitHubAWSInfrastructuretype and topics are labelled automatically from the skill text
Runs in: OpenClaw Claude / Claude Code ChatGPT / Codex Gemini CLI Cursor GitHub Copilot / VS Code Qwen Code Kimi Code CLI Z.ai (GLM) DeepSeek (Deep Code) Mistral Vibe LangChain (deepagents) Goose OpenCode
JSON
Technical rating
B
75/100
safety, quality, tests
Safety 60%
92
Quality 40%
49
Run on models
none yet
Process rating
C
53/100
Has gaps
Result and completion w 14
0
Inputs and preconditions w 11
0
Failures and branches w 10
0
the three weakest of ten parameters · all ten

What is at stake

Medium-severity findings: the skill is probably honest, but read what alarmed the scanner.

Dangerous commands medium severity

Below is the worst case for this category. The finding here is medium: the guard saw a sign, not a proof.

If you install

The skill contains commands that delete files, rewrite disks or execute code fetched from the network. The agent may run them without asking if it believes the instructions require it.

For the author

Replace destructive commands with safe equivalents that ask for confirmation, scope them to one folder, and stop piping curl into a shell: pin a version and a checksum.

How to improve

  1. Say in the description WHEN to use the skill ("use when…", example requests): that is the agent's main cue.
  2. The SKILL.md body is over 5,000 tokens: move reference detail into references/ and load it when needed.
For the model run — optional
  • Your own cases (evals/evals.json, 4–6 real requests with expected answers): the full check would then run those instead of a model-drafted suite.
  • A spec.yaml with trigger phrases and assertions — a behaviour contract for CI; `skilltest init` writes a template.

Guard findings · 4

✓ No critical or high findings

Medium and low: 4
  • medium Dangerous commands cmd-persistence SKILL.md:3
    Persistence mechanism (cron / launchd / scheduled task / autorun registry) (documentation of a security skill)
    description: Cron expression explainer, validator, and converter. Translates any cron expression into plain English ("0 */6 * * *" → "Every 6 hours, at minute 0"), shows the next 5 scheduled run times
    security skill

A further 3 matches are quotations in this security skill's documentation and are not counted as findings.

Files scanned: 2. Evidence is masked. Grey chips explain why severity was lowered.

Against the Agent Skills spec

  • warning frontmatter-yaml SKILL.md: the frontmatter is not valid YAML (YAML parse error: Nested mappings are not allowed in compact mappings at line 2, column 14: description: Cron expression explainer, validator, and converter. Translates an… ^ ); fields were read line by line. The usual cause is a colon inside an unquoted value
  • warning name-format name should be kebab-case (lowercase letters, digits, hyphens)
  • warning description-no-when description does not say WHEN to use the skill (no "use when")
  • warning body-long SKILL.md body ≈ 6739 tokens (recommended < 5000); move details to references/
  • note frontmatter-key unknown frontmatter key "homepage"

Process rating: all ten parameters 53/100

  • 0Result and completion. Does not say what the result is
  • 0Inputs and preconditions. Does not say what the process needs to start
  • 0Failures and branches. Linear process with no failure handling
  • 0Progress reporting. Says nothing while it works
  • 40Consistency. Frontmatter name (Cron Explainer) differs from the folder (phy-cron-explainer)
  • 70When it triggers. States when to use, but not when not to
  • 70Execution cost. Instruction body is 6739 tokens
  • 100Tools and files. No external tools needed
  • 100Steps. 9 steps
  • 100Running it twice. No mutating operations

Everything here is measured from the skill text rather than judged by a model, so the numbers are checkable. A parameter weighs more when it is a more common reason for the process to stall.

Quality signals

  • +4Description does not say when NOT to use the skill (false activations)
  • +3Description length 982: 120–800 characters recommended
  • +3Output format is not stated: the model decides each time
  • +2Single-language instructions
  • +5Description quotes 10 example trigger phrases
  • +4Structure: 13 headings
  • +3Step-by-step instructions: 9 items
  • +4Has examples (9 code blocks)
  • +1License stated

Quality base 70; lint remarks subtract, signals add up to 100. Result: 49.

External checks

ClawHub: suspicious
This cron helper is mostly aligned with its purpose, but it quietly includes an automatic package install that contradicts its local-only claim.
LLM: suspicious (high) · VirusTotal: · 29 May 2026