CronSpell

Explain a cron expression

explain_cron

Read-onlyIdempotent

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.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "expression": "<expression>"
    },
    "name": "explain_cron"
  }
}

Input Schema

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

Output Schema

Name	Required	Description	Default
`notes`	No
`format`	No
`version`	Yes
`expression`	Yes
`normalized`	No
`dayMatching`	No
`description`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 22, 2026

TDQS

A4.3/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description adds value beyond that: it discloses that extra 'surprising rules' notes are returned, that invalid input yields isError with a reason, and that results come from the same engine as the GET endpoint.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Four short sentences, front-loaded with the core transform and example, then the supplementary output notes and error behavior. Nothing is redundant.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a single-parameter read-only tool with a rich schema and an output schema, the description covers everything an agent needs: what it returns, the error contract, and the source of truth. No important invocation detail is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% and the schema already documents the expression formats (including 6-field seconds and @-shorthands). The description's example adds only a small amount beyond that, so baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb+resource ('Explain a cron expression in plain English') and anchors it with a concrete input→output example. The transform nature (expression → English sentence + notes) clearly separates it from siblings like validate_cron and next_cron_runs.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The example and the 'invalid expressions return isError with the reason' clause make the intended use clear. It doesn't explicitly route the agent away from validate_cron or next_cron_runs, so the alternative-selection guidance is implied rather than stated.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

All CronSpell tools Inspect

Try in Browser

Claude Code, inside the Godot 4 editorFlockbay puts an AI agent in the real Godot 4 editor: it writes GDScript, runs your game and fixes what breaks. Free, or bring your own Claude Code or Codex.flockbay.comAd

Glama MCP Gateway

Add one secure layer between your agents and this server.

Resources

Need Help?