Cron expression validate

cron-expression-validate · version 1.0.0 · Other utilities · free, no key needed

Check whether a five-field cron expression is supported and return a validity flag with a reason code.

Use when you need to: validate cron expression · check cron syntax · is this five field cron valid.

Decide before calling

Read the versioned contract and the supported scope below. Reuse cron-expression-validate@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-expression-validate@1.0.0 for validate cron expression. 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

• validate cron expression
• check cron syntax
• is this five field cron valid
• lint a cron schedule
• verify cron field ranges
• detect unsupported cron syntax

Not supported

• compute run times
• six-field cron with seconds
• 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.
• Validates POSIX.1-2024 crontab utility INPUT FILES section fields plus Vixie cron 3.0pl1 ranges, lists, and steps.
• A syntactically invalid, well-typed expression returns valid false rather than throwing.

Input

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

Output

• expression (string, required): min length 1; max length 128
• valid (boolean, required)
• reason (string or null, required)
• 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": "*/15 * * * *"
}

Response:

{
  "result": {
    "expression": "*/15 * * * *",
    "valid": true,
    "reason": null,
    "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-expression-validate",
  "version": "1.0.0",
  "input": {
    "expression": "*/15 * * * *"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/cron-expression-validate/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"expression":"*/15 * * * *"}'

The machine-readable contract is at /v1/tools/cron-expression-validate/versions/1.0.0.

CLI

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

Get the client at /clients/cli/.

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