Cron Explainer

Explain a cron expression in plain English and list its next run times.

Pay by wallet (x402) cron-explain

Example

Input

{
  "timezone": "Europe/Stockholm",
  "cron_expression": "0 9 * * 1-5"
}

Answer

{
  "is_valid": true,
  "timezone": "Europe/Stockholm",
  "next_runs": [
    "2026-03-09T09:00:00.000Z",
    "2026-03-10T09:00:00.000Z",
    "2026-03-11T09:00:00.000Z",
    "2026-03-12T09:00:00.000Z",
    "2026-03-13T09:00:00.000Z"
  ],
  "explanation": "At 9:00, Monday through Friday",
  "cron_expression": "0 9 * * 1-5",
  "field_breakdown": [
    {
      "field": "minute",
      "value": "0",
      "meaning": "at 0"
    },
    {
      "field": "hour",
      "value": "9",
      "meaning": "at 9"
    },
    {
      "field": "day of month",
      "value": "*",
      "meaning": "every value"
    },
    {
      "field": "month",
      "value": "*",
      "meaning": "every value"
    },
    {
      "field": "day of week",
      "value": "1-5",
      "meaning": "range 1-5"
    }
  ]
}

Inputs

Field	Type	Required	What it is
`num_next`	integer	No	Number of next runs (default 5)
`timezone`	string	No	—
`cron_expression`	string	Yes	Cron expression (5-7 fields)

Output fields

How reliably each field appears in a successful answer.

Field	Type	Appears
`is_valid`	boolean	Always (present in every successful answer)
`next_runs`	array	Always (present in every successful answer)
`explanation`	string	Always (present in every successful answer)
`field_breakdown`	array	Always (present in every successful answer)

How to call it

The same tool through each route. MCP clients reach it through Strale’s server at https://api.strale.io/mcp; the call below is what the agent sends.

# Needs an API key. max_price_cents caps what this call may cost.
curl -X POST https://api.strale.io/v1/do \
  -H "Authorization: Bearer $STRALE_API_KEY" \
  -H 'Content-Type: application/json' \
  -d '{
    "capability_slug": "cron-explain",
    "inputs": {
      "timezone": "Europe/Stockholm",
      "cron_expression": "0 9 * * 1-5"
    },
    "max_price_cents": 2
  }'

{
  "tool": "strale_execute",
  "arguments": {
    "slug": "cron-explain",
    "inputs": {
      "timezone": "Europe/Stockholm",
      "cron_expression": "0 9 * * 1-5"
    },
    "max_price_cents": 2
  }
}

import { Strale } from "straleio";

const strale = new Strale({ apiKey: process.env.STRALE_API_KEY! });
const result = await strale.do({
  capability_slug: "cron-explain",
  inputs: {
    "timezone": "Europe/Stockholm",
    "cron_expression": "0 9 * * 1-5"
  },
  max_price_cents: 2,
});

import os
from straleio import Strale, DoRequest

strale = Strale(api_key=os.environ["STRALE_API_KEY"])
result = strale.do(DoRequest(
    capability_slug="cron-explain",
    inputs={
        "timezone": "Europe/Stockholm",
        "cron_expression": "0 9 * * 1-5",
    },
    max_price_cents=2,
))

# No account. The first request answers 402 with the price in USDC;
# an x402 client pays it from your wallet and repeats the request.
curl -i 'https://api.strale.io/x402/v2/cron-explain?timezone=Europe%2FStockholm&cron_expression=0+9+*+*+1-5'

Limitations

Non-standard cron extensions may be misread
Explains standard 5-field cron syntax — non-standard extensions (seconds, years, L/W/# operators) may not be fully explained
What to do instead: Specify the cron implementation (Quartz, AWS EventBridge, systemd) for accurate explanation of non-standard fields

Related tools

Regex Generator €0.05