cron-explainer
RemoteAbout cron-explainer
cron-explainer is a pay-per-call API for parsing cron expressions, describing their schedule in English, and returning upcoming fire times. It is intended for developers working with five-field cron syntax and IANA time zones.
Key features
- 01Parse five-field cron expressions
- 02Generate short English descriptions
- 03Return upcoming fire times
- 04Interpret IANA time zones
- 05Report validation errors and schedule flags
Use cases
- 01Check when a cron job will run next
- 02Explain an unfamiliar cron expression
- 03Inspect a schedule across time zones
MCP support
The MCP server exposes an `explain_cron` tool over Streamable HTTP at `/mcp`. Requests require an `x-api-key` header, and MCP calls use the same billing as the REST API.
Configuration
Remote servers need no local install. Pick your client, then copy the config or install in one click.
https://cron-explainer.cron-explainer-prod.workers.dev/mcpclaude mcp add --transport http idoazacalls-cron-explainer https://cron-explainer.cron-explainer-prod.workers.dev/mcp{"mcpServers":{"idoazacalls-cron-explainer":{"type":"http","url":"https://cron-explainer.cron-explainer-prod.workers.dev/mcp"}}}Open in Cursor{"servers":{"idoazacalls-cron-explainer":{"type":"http","url":"https://cron-explainer.cron-explainer-prod.workers.dev/mcp"}}}Open in VS Code{"mcpServers":{"idoazacalls-cron-explainer":{"type":"http","url":"https://cron-explainer.cron-explainer-prod.workers.dev/mcp"}}}{"mcpServers":{"idoazacalls-cron-explainer":{"serverUrl":"https://cron-explainer.cron-explainer-prod.workers.dev/mcp"}}}Run commands in a terminal; paste JSON into the client’s MCP config and restart. Servers that need sign-in will prompt on first connect.
Tools
1| Parameter | Type | Required | Description |
|---|---|---|---|
| n | integer | No | Number of upcoming fire times to return. |
| tz | string | No | IANA timezone (e.g. 'Europe/Lisbon'). Defaults to UTC. |
| cron | string | Yes | POSIX/Vixie cron expression (5 fields, e.g. '*/15 * * * *'). |
Details
From the project READMEcron-explainer
A tiny pay-per-call API that parses cron expressions, returns the next N fire times, and produces a short English description. Timezone-aware (IANA).
Live: https://cron-explainer.cron-explainer-prod.workers.dev/ Pricing: 0.01 EUR per successful call, prepaid via Stripe Checkout in packs of 500 / 5,000 / 50,000 calls. Non-2xx responses are refunded. No subscription. Keys never expire.
Quick start
- Get a key at https://cron-explainer.cron-explainer-prod.workers.dev/ (Stripe Checkout, €5 minimum).
- Copy the key — it's shown exactly once.
- Call the API:
curl -X POST https://cron-explainer.cron-explainer-prod.workers.dev/v1/explain \
-H "content-type: application/json" \
-H "x-api-key: $YOUR_KEY" \
-d '{"cron":"0 9 * * 1-5","tz":"Europe/Lisbon","n":3}'
Response:
{
"input": {"cron":"0 9 * * 1-5","tz":"Europe/Lisbon","n":3},
"valid": true,
"description": "At 09:00, Monday through Friday",
"next": ["2026-04-24T08:00:00.000Z","2026-04-27T08:00:00.000Z","2026-04-28T08:00:00.000Z"],
"flags": {"dst_transition_ahead": false, "ambiguous": false, "notes": []},
"errors": []
}
Check remaining balance:
curl -H "x-api-key: $YOUR_KEY" \
https://cron-explainer.cron-explainer-prod.workers.dev/v1/balance
MCP
The server is listed on the official MCP registry as
io.github.IdoAzaCalls/cron-explainer with a Streamable HTTP endpoint at
POST /mcp. It exposes one tool, explain_cron. Pass your x-api-key as
an HTTP header on the MCP transport; billing is identical to the REST path.
Registry entry: https://registry.modelcontextprotocol.io/v0/servers?search=cron-explainer
Endpoints
| Method | Path | Purpose |
|---|---|---|
POST | /v1/explain | Parse + describe + next fire times (billed) |
GET | /v1/balance | Remaining balance for an x-api-key |
POST | /v1/checkout | Create a Stripe Checkout Session |
GET | /v1/schema | JSON Schema for request/response |
POST | /mcp | MCP Streamable HTTP (JSON-RPC 2.0) |
GET | /.well-known/mcp.json | Static tool manifest |
GET | /health | Liveness probe |
GET | /legal/{tos,privacy,disclaimer,notices} | Legal docs |
Limits
- Cron: 5-field POSIX/Vixie syntax (minute, hour, day-of-month, month, day-of-week).
- Timezones: IANA names (e.g.
Europe/Lisbon,America/Los_Angeles). Defaults toUTC. nclamps to[1, 100].- Best-effort accuracy. See
/legal/disclaimerfor warranty terms. - Zero PII: inputs are cron strings and IANA timezones only. Request and response bodies are never logged.
Stack
TypeScript on Cloudflare Workers. Cron parsing via
croner (MIT). English descriptions via
cronstrue (MIT). Full NOTICE
text at /legal/notices.
Contact
[email protected] — billing issues, bug reports, custom pricing.
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