MCP HeartbeatTHE MCP OBSERVATORY
Public workspace

Explore

Evidence for your next connection.

Independent measurements of remote MCP servers. Every observation has a timestamp.

Read-only probes

MCP server · Automation & workflows

CronSpell

By cronspell.mike-tusa.workers.dev Verified namespace

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

Website
Connect to CronSpell
Checks passed
13 / 22

1 failed · 8 not measured

Median response
89 ms

Median of successful probes over 7 days

30-day uptime
Not measured

Share of countable probes over 30 days, including daily rollups. Auth challenges are excluded.

Discovered tools
4

Tool definitions returned by this server

Independent monitoring

Health & checks

Status history

Outdated check

Last connection measurement is over 24 hours old. Current availability is unknown.

Last checked
Check summary by test group
Test areaPassedFailedUnmeasured
ConnectionCan a client connect and discover tools?
500
Reliability & speedDoes it respond consistently and quickly?
004
Access & authenticationWhat is required to use this server?
102
Tool qualityAre the tool definitions usable by an agent?
400
Publisher identityCan the publisher be traced to its source?
312

Unmeasured means there is not enough evidence to decide. How these checks work

Inspect individual checks 22 recorded

Core

  • Pass
    Reachable

    Latest probe returned HTTP 200 in 89 ms.

  • Pass
    Valid handshake

    protocolVersion 2025-11-25, serverInfo.name cronspell.

  • Pass
    Lists tools

    tools/list returned 4 tools.

  • Pass
    Current protocol

    Negotiated 2025-11-25. The bar is 2025-06-18 or newer.

  • Pass
    HTTPS

    The endpoint URL is https.

Performance

  • Not measured
    Fast (p50)

    Median latency 89 ms over 1 samples in 7 days. The bar is 1000 ms. Need at least 5 samples.

  • Not measured
    Consistent (p95)

    95th percentile 89 ms over 1 samples in 7 days. The bar is 3000 ms. Need at least 20 samples.

  • Not measured
    Reliable (uptime)

    1 of 1 attempts returned a tool list in 30 days (100%). The bar is 99%. Need at least 30 samples.

  • Not measured
    Stable tool list

    Fewer than two successful probes in 30 days, so tool-list stability is not measured.

Access

  • Pass
    Open access

    tools/list succeeded with no credential, and the record declares none.

  • Not measured
    Standard auth

    Auth is not required, so the OAuth metadata check does not apply.

  • Not measured
    Free tier cited

    No publisher quote has been checked.

Tools

  • Pass
    Tools described

    Every tool description is at least 20 characters.

  • Pass
    Valid input schemas

    Every inputSchema is a JSON Schema object.

  • Pass
    Parameters documented

    12 of 12 parameters have a description (100%). The bar is 80%.

  • Pass
    Safety hints

    Every tool sets readOnlyHint or destructiveHint.

Publisher

  • Pass
    Verified namespace

    Listed in the Official MCP Registry.

  • Pass
    Website matches publisher

    The website host matches the reverse-domain namespace.

  • Fail
    Source repo linked

    No repository URL is on file.

  • Not measured
    Repo owner matches

    This namespace is not an io.github login, so the owner comparison does not apply.

  • Pass
    Recently updated

    Updated 2026-10-22T05:51:17.166645Z, within 180 days.

  • Not measured
    Open-source licence

    No GitHub repository to ask about a licence.

Start using CronSpell

Connect to this server

Choose your client, copy the configuration, then enable the server in your client’s MCP settings.

Run this command in your terminal, then restart Claude Code.

Claude Code

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

Capabilities

Tools 4

cron_runs_between

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.

Discovered
explain_cron

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.

Discovered
next_cron_runs

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.

Discovered
validate_cron

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.

Discovered

Recent measurements

Probe history

View status
Latest stored probes. Raw probe rows are kept for 14 days.
CheckedResultResponseTools
Connected89 ms4

Related servers

All alternatives

Same function and industry, ranked by checks passed then median latency.

Explore alternatives to CronSpell