API, MCP and link monitoring

The same check as on the start page – from your own code, straight from Claude, ChatGPT or Cursor, and as a watchdog that speaks up when a link suddenly leads somewhere else.

Free during the beta. A free tier stays afterwards. Before paid plans arrive, we announce them at least 30 days in advance.

What you get

MCP without a key: Check links from any MCP-capable assistant, up to 60 checks per hour.
API with a key: REST API and MCP with 1,000 checks per day.
Watch with a key: Up to 10 URLs, checked every 6 hours. When the status code, final destination, number of redirects or a detected JavaScript target changes, you get an event – via Atom feed, webhook, API and MCP.

Create a key

An e-mail address is all it takes, there is no confirmation mail. The key appears immediately and only once – together with ready-to-paste setup commands.

Connect via MCP

LinkSniffer is a remote MCP server (Streamable HTTP) at https://www.linksniffer.de/mcp. Without a key you get the checking tools, with a key monitoring as well.

Claude (web and desktop)

Settings → Connectors → Add custom connector → enter https://www.linksniffer.de/mcp as URL. Custom headers cannot be set there, so this connector runs without a key, i.e. with the checking tools only.

Claude Code

claude mcp add --transport http linksniffer https://www.linksniffer.de/mcp \
  --header "Authorization: Bearer YOUR_KEY"

Cursor and other clients

{
  "mcpServers": {
    "linksniffer": {
      "type": "http",
      "url": "https://www.linksniffer.de/mcp",
      "headers": { "Authorization": "Bearer YOUR_KEY" }
    }
  }
}

The tools

inspect_url: Check one URL: status, every redirect, meta refresh, detected JavaScript jumps, headers.
inspect_urls: Up to 10 URLs at once, one line per URL.
add_monitor: Start monitoring a URL.
list_monitors · get_monitor: Monitored URLs with current state and history.
check_monitor_now: Check right away instead of waiting for the schedule.
recent_changes: The latest confirmed changes.
remove_monitor · account_status: Stop monitoring · quota and usage.

REST API

curl -s https://www.linksniffer.de/v1/inspect \
  -H "Authorization: Bearer YOUR_KEY" \
  -H "content-type: application/json" \
  -d '{"url":"https://example.com","userAgent":"mobile"}'

POST /v1/inspect: Check one URL (url, method, userAgent, followRedirects).
GET · POST /v1/monitors: List · create monitors (url, label, userAgent, compare).
GET · DELETE /v1/monitors/:id: State and history · stop monitoring.
POST /v1/monitors/:id/check: Check now.
GET /v1/events: Confirmed changes, newest first.
GET · PATCH · DELETE /v1/me: Quota and usage · set a webhook · delete the key and all its data.

The full description is available as OpenAPI at /v1/openapi.json – which also lets you add LinkSniffer as an action to a custom GPT.

How monitoring works

What counts as a change: status code, final destination (path, without query string), number of redirects and the hosts of detected JavaScript redirects. The query string is left out on purpose, because tracking chains append a new click ID on every request. To compare complete URLs, create the monitor with "compare": "full".
No false alarms from blips: a deviation only counts as a change once a second check a few minutes later confirms it.
Notifications: as an Atom feed (the address is shown when you sign up), via webhook with an HMAC signature (X-LinkSniffer-Signature, set up with PATCH /v1/me) and through API and MCP. E-mail notifications will follow.

Terms of use (beta)

Only publicly reachable addresses may be checked. Load and attack testing is not allowed, nor is circumventing the limits, e.g. with many keys.
Your key is personal and must be kept secret. We store only a hash of it; a lost key cannot be recovered, only replaced by a new one.
During the beta there is no commitment regarding availability or response time. Results reflect what the checked server answered to our server.
Keys may be blocked without notice in case of abuse.
We announce changes to these terms and the introduction of paid plans at least 30 days in advance on this page. A free tier will remain.
You can delete your key yourself at any time (DELETE /v1/me) or ask us to delete it by e-mail to kontakt@linksniffer.de.

Version of 11 September 2026. The data processed is described in the privacy policy, section 5. The German version is binding.