# CronSpell (remote · cronspell.mike-tusa.workers.dev)

Validate and explain cron expressions; list next/previous run times in any time zone, DST-aware.

- Trust score: 72/100 (medium)
- Change this week: +4
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-11-05

## Components

- remote · `cronspell.mike-tusa.workers.dev`: 72/100 (this document), [markdown](https://verifymcp.io/servers/dev-workers-mike-tusa-cronspell-cronspell/cronspell.md), [page](https://verifymcp.io/servers/dev-workers-mike-tusa-cronspell-cronspell/cronspell)

## Channel facts

- Endpoint: `https://cronspell.mike-tusa.workers.dev/mcp`
- Transports: `streamable-http`
- Auth: `none`
- Version: `0.1.0`

## Trust breakdown

How this component scores in each security and reliability category. Every signal is checked automatically against the live server, and we only credit what we can confirm. Scores are 0–100 per category. Scoring method: https://verifymcp.io/docs/scoring (what has changed: https://verifymcp.io/docs/scoring/changelog)

Scored 2026-11-05.

- **Endpoint Security**: 63/100
  - The endpoint's TLS certificate is valid, in date, and uses a strong key.
  - No authorisation is required to call this server. Nothing on it is marked destructive, but we can't show that an anonymous caller can only read: full credit needs the server to list at least one tool and every tool to be verifiably read-only. We use a best-effort check of tool names and descriptions to tell read-only tools from tools that change things, so some genuinely read-only tools may not get full credit. Names that start with a read verb (get, list, read, search and similar) and accurate readOnlyHint annotations help. Meet that to earn full credit, or require authorisation.
  - HTTPS enforcement could not be verified: the plaintext port answered with HTTP 405, which proves neither a plaintext path nor enforcement.
  - HSTS check failed: the Strict-Transport-Security header is absent.
  - DNSSEC check failed: this domain isn't protected by DNSSEC.
- **Transport & Reachability**: 100/100
  - Verified streamable-http transport via a live MCP handshake.
- **Schema Quality & AI Usability**: 67/100
  - AI-judged instruction clarity (excellent).
  - Context-footprint check failed: tool/resource definitions use about 1057 tokens (~264/item across 4 items; 4 tools + 0 resources), over budget; trim descriptions and params.
  - Usage-examples check failed: none of the tools include examples.
- **Stability & Change Management**: 47/100
  - Stability observed for 14 of 30 days with no destabilising changes; credit accrues until the full window elapses.
- **Tool Coverage**: 100/100
  - 100% of tools have a non-trivial description (not blank, and not just the tool's name).
  - 100% of tool parameters carry a description.
  - Structured output schemas are declared (100% of tools); any adoption earns full credit.
- **Tool Safety**: 100/100
  - No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.
  - We read all 4 captured tool definition(s), and no name or description among them implies an irreversible operation.
  - An AI judge read all 5 captured unit(s) of tool text and found none that tries to manipulate the model reading it.
- **Capabilities**: 100/100
  - Implements a current MCP spec version (2026-07-28).

## Install

### How do I install the CronSpell MCP server?

CronSpell is a hosted endpoint at https://cronspell.mike-tusa.workers.dev/mcp, so there is nothing to install locally. Ready-made configuration for Claude, Cursor, VS Code, Codex and 5 more is on this page, copied from each client's own documentation.

### Claude

```bash
claude mcp add --transport http dev-workers-mike-tusa-cronspell-cronspell 'https://cronspell.mike-tusa.workers.dev/mcp'
```

### Cursor

```json
{
  "mcpServers": {
    "dev-workers-mike-tusa-cronspell-cronspell": {
      "url": "https://cronspell.mike-tusa.workers.dev/mcp"
    }
  }
}
```

### VS Code

```json
{
  "servers": {
    "dev-workers-mike-tusa-cronspell-cronspell": {
      "type": "http",
      "url": "https://cronspell.mike-tusa.workers.dev/mcp"
    }
  }
}
```

### Codex

```toml
[mcp_servers.dev-workers-mike-tusa-cronspell-cronspell]
url = "https://cronspell.mike-tusa.workers.dev/mcp"
```

### opencode

```json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "dev-workers-mike-tusa-cronspell-cronspell": {
      "type": "remote",
      "url": "https://cronspell.mike-tusa.workers.dev/mcp",
      "enabled": true
    }
  }
}
```

### OpenClaw

```bash
openclaw mcp add dev-workers-mike-tusa-cronspell-cronspell --url 'https://cronspell.mike-tusa.workers.dev/mcp' --transport streamable-http
```

### Hermes

```yaml
mcp_servers:
  dev-workers-mike-tusa-cronspell-cronspell:
    url: "https://cronspell.mike-tusa.workers.dev/mcp"
```

### Netclaw

```json
{
  "McpServers": {
    "dev-workers-mike-tusa-cronspell-cronspell": {
      "Transport": "http",
      "Url": "https://cronspell.mike-tusa.workers.dev/mcp"
    }
  }
}
```

### Vellum

```bash
assistant mcp add dev-workers-mike-tusa-cronspell-cronspell -t streamable-http -u 'https://cronspell.mike-tusa.workers.dev/mcp'
```

### Other

```json
{
  "mcpServers": {
    "dev-workers-mike-tusa-cronspell-cronspell": {
      "type": "http",
      "url": "https://cronspell.mike-tusa.workers.dev/mcp"
    }
  }
}
```

The mcpServers block is a cross-client convention. Remote transports vary, so check your client's docs.

## Changelog

Every change recorded for this component, newest first. Days that predate change tracking, or that we cannot explain, say so: "we were watching and nothing happened" and "we were not watching" are different claims.

### 2026-11-05 (score 72, +1)

No change was recorded against any check on this day. Stability & Change Management went from 43 to 47. That category is still filling its 30-day observation window: 13 days of observed history at the previous scan, 14 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-11-03 (score 71, +1)

No change was recorded against any check on this day. Stability & Change Management went from 37 to 40. That category is still filling its 30-day observation window: 11 days of observed history at the previous scan, 12 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-11-01 (score 70, +1)

No change was recorded against any check on this day. Stability & Change Management went from 30 to 33. That category is still filling its 30-day observation window: 9 days of observed history at the previous scan, 10 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-30 (score 69, +1)

No change was recorded against any check on this day. Stability & Change Management went from 23 to 27. That category is still filling its 30-day observation window: 7 days of observed history at the previous scan, 8 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-27 (score 68, +1)

No change was recorded against any check on this day. Stability & Change Management went from 13 to 17. That category is still filling its 30-day observation window: 4 days of observed history at the previous scan, 5 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-25 (score 67, +1)

No change was recorded against any check on this day. Stability & Change Management went from 7 to 10. That category is still filling its 30-day observation window: 2 days of observed history at the previous scan, 3 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-23 (score 66, +1)

- [functional improvement] Stability: unverified → 0.03

### 2026-10-22 (score 65)

First indexed and scored.

## MCP tools (4)

### `validate_cron` (~145 tokens)

Validate a cron expression

Check whether a cron expression is valid. Returns valid true with the expanded values of every field (minute, hour, day of month, month, day of week, and seconds for 6-field expressions), or valid false with an error code, the field at fault and a message. Detects schedules that can never run (e.g. February 30). Read-only. Same engine as GET /api/validate.

Input parameters:

- `expression` (string, required): Cron expression, e.g. "0 9 * * 1-5", "*/15 * * * *", "0 30 8 * * *" (6 fields = leading seconds) or "@daily".

Output parameters:

- `dayMatching` (string)
- `description` (string)
- `error` (object)
- `expression` (string)
- `fields` (object)
- `format` (string)
- `normalized` (string)
- `valid` (boolean)
- `version` (string)

### `explain_cron` (~142 tokens)

Explain a cron expression

Explain a cron expression in plain English, e.g. "0 9 * * 1-5" → "At 09:00, on Monday through Friday." Also returns notes on cron rules that often surprise people (day-of-month OR day-of-week, seconds field, shorthand expansion). Invalid expressions return isError with the reason. Read-only. Same engine as GET /api/explain.

Input parameters:

- `expression` (string, required): Cron expression, e.g. "0 9 * * 1-5", "*/15 * * * *", "0 30 8 * * *" (6 fields = leading seconds) or "@daily".

Output parameters:

- `dayMatching` (string)
- `description` (string)
- `expression` (string)
- `format` (string)
- `normalized` (string)
- `notes` (array)
- `version` (string)

### `next_cron_runs` (~276 tokens)

List next (or previous) cron run times

List the next (or, with direction "previous", the most recent past) run times of a cron expression in an IANA time zone, DST-aware. Each run has the local time with its UTC offset, the UTC time, unix seconds and weekday. Default 5 runs, max 20; searches up to 50 years. Read-only. Same engine as GET /api/next and GET /api/previous.

Input parameters:

- `count` (integer): How many runs (1-20).
- `direction` (string): "next" (default) or "previous" (most recent first).
- `expression` (string, required): Cron expression, e.g. "0 9 * * 1-5", "*/15 * * * *", "0 30 8 * * *" (6 fields = leading seconds) or "@daily".
- `from` (string): Start point (exclusive); default now. ISO 8601 with Z or an offset (2026-11-01T09:00:00Z), a local time read in the time zone (2026-11-01T09:00), or unix seconds.
- `timezone` (string): IANA time zone the schedule runs in, e.g. "America/Denver", "Europe/London". Default UTC.

Output parameters:

- `complete` (boolean)
- `description` (string)
- `direction` (string)
- `expression` (string)
- `from` (string)
- `normalized` (string)
- `notes` (array)
- `runs` (array)
- `timezone` (string)
- `version` (string)

### `cron_runs_between` (~282 tokens)

List cron runs between two times

List every run of a cron expression between start and end (both inclusive) in an IANA time zone, DST-aware, oldest first. Default limit 20, max 100; truncated is true when there are more. Read-only. Same engine as GET /api/between.

Input parameters:

- `end` (string, required): Window end (inclusive). ISO 8601 with Z or an offset (2026-11-01T09:00:00Z), a local time read in the time zone (2026-11-01T09:00), or unix seconds.
- `expression` (string, required): Cron expression, e.g. "0 9 * * 1-5", "*/15 * * * *", "0 30 8 * * *" (6 fields = leading seconds) or "@daily".
- `limit` (integer): Max runs to return (1-100).
- `start` (string, required): Window start (inclusive). ISO 8601 with Z or an offset (2026-11-01T09:00:00Z), a local time read in the time zone (2026-11-01T09:00), or unix seconds.
- `timezone` (string): IANA time zone the schedule runs in, e.g. "America/Denver", "Europe/London". Default UTC.

Output parameters:

- `complete` (boolean)
- `description` (string)
- `end` (string)
- `expression` (string)
- `normalized` (string)
- `notes` (array)
- `runs` (array)
- `start` (string)
- `timezone` (string)
- `truncated` (boolean)
- `version` (string)

## Diagnostics

Captured diagnostic sections: TLS, DNSSEC, Authorisation, Transports. The full working is on the page: https://verifymcp.io/servers/dev-workers-mike-tusa-cronspell-cronspell/cronspell#diagnostics

## Score history

- 2026-11-05: 72
- 2026-11-04: 71
- 2026-11-03: 71
- 2026-11-02: 70
- 2026-11-01: 70
- 2026-10-31: 69
- 2026-10-30: 69
- 2026-10-29: 68
- 2026-10-28: 68
- 2026-10-27: 68
- 2026-10-26: 67
- 2026-10-25: 67
- 2026-10-24: 66
- 2026-10-23: 66
- 2026-10-22: 65

## Common questions

### What is the CronSpell MCP server?

CronSpell is an MCP server listed in the public MCP registry as dev.workers.mike-tusa.cronspell/cronspell. Validate and explain cron expressions; list next/previous run times in any time zone, DST-aware. This page covers its hosted endpoint (https://cronspell.mike-tusa.workers.dev/mcp).

### Is the CronSpell MCP server safe to use?

CronSpell scores 72 out of 100 on VerifyMCP. That is a record of what we were able to check automatically, not an endorsement. The category breakdown on this page shows every signal behind the number, including the ones we could not confirm.

### What tools does the CronSpell MCP server expose?

CronSpell exposes 4 tools: validate_cron, explain_cron, next_cron_runs, cron_runs_between. Their descriptions and schemas cost roughly 845 tokens of context every time the server is loaded.

### Does the CronSpell MCP server require authentication?

No. We connected to CronSpell without credentials and it answered, so anything it exposes is reachable by anyone who knows the address.

### Is the CronSpell MCP server still maintained?

CronSpell is still listed as active in the MCP registry. We last reached this channel on 5 November 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.

### What did VerifyMCP test on the CronSpell MCP server?

VerifyMCP ran 12 checks on CronSpell, covering TLS certificate, Authorization, HSTS header, DNSSEC and 8 more. One item could not be completed, a gap on our side rather than a finding about CronSpell: HTTPS. Supply Chain Security and Provenance & Transparency do not apply to a hosted endpoint, so they were not tested. The score does not measure everything, and the scoring documentation lists what it leaves out.

## Links

- Remote endpoint: https://cronspell.mike-tusa.workers.dev/mcp
- Website: https://cronspell.mike-tusa.workers.dev/
- Changelog RSS feed: https://verifymcp.io/servers/dev-workers-mike-tusa-cronspell-cronspell/cronspell.xml
- Changelog JSON feed: https://verifymcp.io/servers/dev-workers-mike-tusa-cronspell-cronspell/cronspell/changelog.json
- Trust report (JSON): https://verifymcp.io/servers/dev-workers-mike-tusa-cronspell-cronspell/cronspell.json
- HTML version of this page: https://verifymcp.io/servers/dev-workers-mike-tusa-cronspell-cronspell/cronspell