Cron describe fields

cron-describe-fields · version 1.0.0 · Other utilities · free, no key needed

Parse a five-field cron expression and return each field’s expanded numeric values and wildcard status.

Use when you need to: describe cron fields · explain a cron expression · expand cron numeric values.

Decide before calling

Read the versioned contract and the supported scope below. Reuse cron-describe-fields@1.0.0 when your input, required output and limits match it. Choose another approach for an unsupported operation.

Explain the choice

"I can use cron-describe-fields@1.0.0 for describe cron fields. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

Supported

• describe cron fields
• explain a cron expression
• expand cron numeric values
• show cron minute and hour sets
• parse cron schedule fields
• understand what a cron means

Not supported

• compute run times
• translate cron to natural language prose
• named months or weekdays

Behavior

• Vixie wildcard status is true when a field starts with *, including */n; if either day field starts with *, both day value sets must match; otherwise day matching uses OR.
• Returns five fields in POSIX.1-2024 crontab utility INPUT FILES section order.
• Vixie cron 3.0pl1 lists, ranges, and steps expand to sorted unique integers; weekday 7 normalizes to 0.

Input

• expression (string, required): min length 1; max length 128

Output

• expression (string, required): min length 1; max length 128
• fields (array of object, required): min items 5; max items 5
• standard_version (constant "POSIX.1-2024 crontab utility, INPUT FILES", required)

Limits

• max input bytes: 512
• max expression bytes: 128
• max field items: 60
• max output bytes: 4096

Example

Request input:

{
  "expression": "0 9 * * 1-5"
}

Response:

{
  "result": {
    "expression": "0 9 * * 1-5",
    "fields": [
      {
        "name": "minute",
        "source": "0",
        "wildcard": false,
        "values": [
          0
        ]
      },
      {
        "name": "hour",
        "source": "9",
        "wildcard": false,
        "values": [
          9
        ]
      },
      {
        "name": "day_of_month",
        "source": "*",
        "wildcard": true,
        "values": [
          1,
          2,
          3,
          4,
          5,
          6,
          7,
          8,
          9,
          10,
          11,
          12,
          13,
          14,
          15,
          16,
          17,
          18,
          19,
          20,
          21,
          22,
          23,
          24,
          25,
          26,
          27,
          28,
          29,
          30,
          31
        ]
      },
      {
        "name": "month",
        "source": "*",
        "wildcard": true,
        "values": [
          1,
          2,
          3,
          4,
          5,
          6,
          7,
          8,
          9,
          10,
          11,
          12
        ]
      },
      {
        "name": "day_of_week",
        "source": "1-5",
        "wildcard": false,
        "values": [
          1,
          2,
          3,
          4,
          5
        ]
      }
    ],
    "standard_version": "POSIX.1-2024 crontab utility, INPUT FILES"
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "cron-describe-fields",
  "version": "1.0.0",
  "input": {
    "expression": "0 9 * * 1-5"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/cron-describe-fields/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"expression":"0 9 * * 1-5"}'

The machine-readable contract is at /v1/tools/cron-describe-fields/versions/1.0.0.

CLI

node cli.mjs run cron-describe-fields 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

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