# Agentshelf Cron-5 Expression Validator

> Agentshelf Cron-5 Expression Validator is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.004/call, status unknown (last checked 2026-09-29).

Validates whether a given string is a valid 5-field cron expression

## Facts

- Endpoint: POST https://agentshelf.syntexa.ch/v1/check-cron-5?utm_source=zero.xyz
- Price: $0.004/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agentshelf-cron-5-expression-validator-1b6c2757
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_4l9t_XXBQXGPIXoHzPcYE

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability agentshelf-cron-5-expression-validator-1b6c2757 -d '<json body>'
```

Example prompt: Can you check if '*/5 * * * *' is a valid 5-field cron expression?

## When to prefer this

Use this endpoint when you need a deterministic, programmatic check that a cron string is exactly a 5-field expression (no LLM guessing). Prefer the free sandbox endpoint /v1/sandbox/check-cron-5 first; use this paid endpoint only when the sandbox is unavailable or rate-limited. Ideal for pipelines that must validate user-submitted cron schedules before storing or executing them.

## Known failure modes

- Empty or missing value field returns an error
- String exceeding 20000 characters rejected
- Non-string input may be rejected or mishandled
- 6-field or 7-field cron expressions (with seconds or year) may be flagged as invalid even if otherwise well-formed

## How this service works

Call when an agent needs whether a string is a 5-field cron expression. Exact $0.004 USDC. Prefer unpaid POST /v1/sandbox/check-cron-5 first.

## Output

Returns whether the provided string is a valid 5-field cron expression, indicating if the input conforms to the standard minute, hour, day-of-month, month, and day-of-week format.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "data": {
   "description": "JSON value for schema-check SKUs. Omit it on string checks such as email or IBAN."
  },
  "value": {
   "type": "string",
   "examples": [
    "0 * * * *"
   ],
   "maxLength": 20000,
   "minLength": 1,
   "description": "Value to check. The route description names the format: email, phone, IBAN, postal code, VAT, national id, or similar."
  },
  "schema": {
   "description": "JSON Schema document for schema-check SKUs. Omit it on string checks."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agentshelf-cron-5-expression-validator-1b6c2757/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agentshelf.syntexa.ch](https://www.zero.xyz/host/agentshelf.syntexa.ch/llms.txt)