API Reference

The Watchmint base URL is https://api-watchmint.plxi.us. Every endpoint accepts and returns JSON and is authenticated with your API key.

curl -X POST https://api-watchmint.plxi.us/v1/diff/text \
  -H "X-API-Key: sk_live_..." \
  -H "Content-Type: application/json" \
  -d '{
  "after": "Pro plan: $59/month\nFree trial: 14 days\nSupport: email and chat",
  "before": "Pro plan: $49/month\nFree trial: 14 days\nSupport: email"
}'

Authentication

Send an X-API-Key header with every request. Keys are created and revoked in the dashboard; a key is shown once, when it is created, so store it somewhere safe.

X-API-Key: sk_live_...

Plans & limits

Limits apply per account, not per key: every key on the account (and teammates working in it) shares them. There is a per-minute rate, a cap on requests in flight at once, and a monthly quota. On the Free plan the quota resets on the 1st of each month (UTC); on paid plans it resets on your billing-period anniversary. Requests that fail validation are never charged.

Errors

Errors return JSON with a stable error code, an optional message, and, on rate-limit and monthly-quota 429s, reset_at. A request that returns an error is never charged.

{
  "error": "rate_limit_exceeded",
  "reset_at": "2026-07-22T18:04:00Z"
}

How checks work

A monitor (POST /v1/monitors/create) is checked every every_minutes: at most hourly on Free, every 5 minutes on Starter and every minute on Pro. Each check costs one check, text or visual. A check that can’t read the page is free.

• Baseline. The first check (due as soon as the monitor is made) is what later checks compare against. When a change is found it becomes the new baseline, so each change is reported once.
• Text. The page is fetched and its visible text read, one block per line (scripts, styles and hidden elements left out), or only what selector matches. Spacing doesn’t count, and ignore_selectors and ignore_patterns (regular expressions, matched per line) are taken out first. A page built by script, with no text until it runs, is read in a browser; render: true always does.
• Visual. A screenshot (the whole page unless full_page is false) is shrunk to 400 pixels wide and compared pixel by pixel with the baseline’s. It’s a change when at least threshold percent of the picture differs (1% by default).
• Confirm. With confirm: true, a change is reported only when two checks in a row see it: rotating banners and A/B tests stop alerting.
• Status. active, paused (by you), paused_quota (the month’s checks ran out: it tries again every 10 minutes and resumes by itself in the next period or after a top-up), or failing (three failed checks in a row; it’s still checked and turns active again on the next good check).
• What’s kept. The last 30 snapshots of each monitor and 90 days of changes. Screenshot links last 30 days. Bot checks and CAPTCHA walls aren’t bypassed; they count as failed checks.

Use with AI agents (MCP)

Watchmint is also an MCP server, so Claude and other AI agents can call its main operations as tools (listed below). Tool calls are charged exactly like API calls, to the same plan and quota, and failed calls are free.

https://api-watchmint.plxi.us/mcp

Claude (claude.ai and the desktop app): Settings → Connectors → Add custom connector, then paste the URL above. Claude asks you to sign in with your Plexsicity account; calls are then charged to your own account.

Claude Code, Cursor, VS Code and other clients: send an API key from the dashboard as a header. Calls are charged to the account that owns the key, so a team’s key spends the team’s quota. Clients that only take a bearer token can send Authorization: Bearer sk_live_… instead.

claude mcp add --transport http watchmint https://api-watchmint.plxi.us/mcp \
  --header "X-API-Key: sk_live_..."

## Watchmint
- To be told when a page changes, call `watch_page` instead of re-reading the page yourself; read what changed later with `get_changes`.
- To see what changed on a page since you last read it, call `compare_page` with the `text` it returned last time.

POST/v1/diff/text

Compare two versions of a text, as a check compares a page: added and removed lines and words, and a unified diff. Costs 1 check.

{
  "after": "Pro plan: $59/month\nFree trial: 14 days\nSupport: email and chat",
  "before": "Pro plan: $49/month\nFree trial: 14 days\nSupport: email"
}

{
  "added": [
    "Pro plan: $59/month",
    "Support: email and chat"
  ],
  "added_lines": 2,
  "added_words": 3,
  "changed": true,
  "credits": 1,
  "diff": "--- before\n+++ after\n@@ -1,3 +1,3 @@\n-Pro plan: $49/month\n+Pro plan: $59/month\n Free trial: 14 days\n-Support: email\n+Support: email and chat\n",
  "diff_truncated": false,
  "removed": [
    "Pro plan: $49/month",
    "Support: email"
  ],
  "removed_lines": 2,
  "removed_words": 1,
  "summary": "2 lines added, 2 removed"
}

curl -X POST https://api-watchmint.plxi.us/v1/diff/text \
  -H "X-API-Key: sk_live_..." \
  -H "Content-Type: application/json" \
  -d '{
  "after": "Pro plan: $59/month\nFree trial: 14 days\nSupport: email and chat",
  "before": "Pro plan: $49/month\nFree trial: 14 days\nSupport: email"
}'

The response is the operation’s result plus credits, what the request was charged. Try it in the Playground. MCP tool: diff_text.

POST/v1/pages/compare

Read a web page now and compare it with text you kept from it before. Nothing is stored. Costs 1 check.

{
  "selector": "h1",
  "text": "The World Wide Web project",
  "url": "https://info.cern.ch/hypertext/WWW/TheProject.html"
}

{
  "added": [
    "World Wide Web"
  ],
  "added_lines": 1,
  "added_words": 0,
  "changed": true,
  "credits": 1,
  "diff": "--- before\n+++ after\n@@ -1 +1 @@\n-The World Wide Web project\n+World Wide Web\n",
  "diff_truncated": false,
  "final_url": "https://info.cern.ch/hypertext/WWW/TheProject.html",
  "removed": [
    "The World Wide Web project"
  ],
  "removed_lines": 1,
  "removed_words": 2,
  "rendered": false,
  "status": 200,
  "summary": "1 line added, 1 removed",
  "text": "World Wide Web",
  "text_truncated": false,
  "url": "https://info.cern.ch/hypertext/WWW/TheProject.html"
}

curl -X POST https://api-watchmint.plxi.us/v1/pages/compare \
  -H "X-API-Key: sk_live_..." \
  -H "Content-Type: application/json" \
  -d '{
  "selector": "h1",
  "text": "The World Wide Web project",
  "url": "https://info.cern.ch/hypertext/WWW/TheProject.html"
}'

The response is the operation’s result plus credits, what the request was charged. Try it in the Playground. MCP tool: compare_page.

POST/v1/monitors/check

Check one of your monitors now instead of waiting for its next scheduled check. Costs 1 check.

{
  "monitor_id": "7c3f1a2e-5b4d-4e8f-9a6b-2d1c0e9f8a7b"
}

{
  "baseline": false,
  "change": null,
  "changed": false,
  "credits": 1,
  "final_url": "https://info.cern.ch/hypertext/WWW/TheProject.html",
  "monitor_id": "7c3f1a2e-5b4d-4e8f-9a6b-2d1c0e9f8a7b",
  "pending_confirmation": false,
  "status": 200,
  "summary": "No change",
  "text_changed": false,
  "visual_changed_pct": null
}

curl -X POST https://api-watchmint.plxi.us/v1/monitors/check \
  -H "X-API-Key: sk_live_..." \
  -H "Content-Type: application/json" \
  -d '{
  "monitor_id": "7c3f1a2e-5b4d-4e8f-9a6b-2d1c0e9f8a7b"
}'

The response is the operation’s result plus credits, what the request was charged. Try it in the Playground. MCP tool: check_now.

POST/v1/monitors/create

Start watching a page: Watchmint checks it on a schedule and tells you when it changes. Costs 0 checks.

{
  "every_minutes": 60,
  "name": "The first web page",
  "url": "https://info.cern.ch/hypertext/WWW/TheProject.html",
  "watch": "text"
}

{
  "credits": 0,
  "monitor": {
    "changes": 0,
    "checks": 0,
    "confirm": false,
    "created_at": "2026-10-31T12:00:00Z",
    "every_minutes": 60,
    "full_page": true,
    "id": "7c3f1a2e-5b4d-4e8f-9a6b-2d1c0e9f8a7b",
    "ignore_patterns": [],
    "ignore_selectors": [],
    "last_change_at": null,
    "last_check_at": null,
    "last_error": null,
    "name": "The first web page",
    "next_check_at": "2026-10-31T12:00:00Z",
    "render": false,
    "selector": null,
    "status": "active",
    "threshold": 1,
    "url": "https://info.cern.ch/hypertext/WWW/TheProject.html",
    "viewport_height": 800,
    "viewport_width": 1280,
    "watch": "text",
    "webhook_id": null
  }
}

curl -X POST https://api-watchmint.plxi.us/v1/monitors/create \
  -H "X-API-Key: sk_live_..." \
  -H "Content-Type: application/json" \
  -d '{
  "every_minutes": 60,
  "name": "The first web page",
  "url": "https://info.cern.ch/hypertext/WWW/TheProject.html",
  "watch": "text"
}'

The response is the operation’s result plus credits, what the request was charged. Try it in the Playground. MCP tool: watch_page.

POST/v1/monitors/list

The account's monitors, newest first, with their status and last check and change. Costs 0 checks.

{
  "limit": 20
}

{
  "credits": 0,
  "monitors": [],
  "total": 0
}

curl -X POST https://api-watchmint.plxi.us/v1/monitors/list \
  -H "X-API-Key: sk_live_..." \
  -H "Content-Type: application/json" \
  -d '{
  "limit": 20
}'

The response is the operation’s result plus credits, what the request was charged. Try it in the Playground. MCP tool: list_watches.

POST/v1/monitors/update

Change a monitor's settings, or pause and resume it. Costs 0 checks.

{
  "monitor_id": "7c3f1a2e-5b4d-4e8f-9a6b-2d1c0e9f8a7b",
  "paused": true
}

{
  "credits": 0,
  "monitor": {
    "every_minutes": 60,
    "id": "7c3f1a2e-5b4d-4e8f-9a6b-2d1c0e9f8a7b",
    "name": "The first web page",
    "status": "paused",
    "url": "https://info.cern.ch/hypertext/WWW/TheProject.html",
    "watch": "text"
  }
}

curl -X POST https://api-watchmint.plxi.us/v1/monitors/update \
  -H "X-API-Key: sk_live_..." \
  -H "Content-Type: application/json" \
  -d '{
  "monitor_id": "7c3f1a2e-5b4d-4e8f-9a6b-2d1c0e9f8a7b",
  "paused": true
}'

The response is the operation’s result plus credits, what the request was charged. Try it in the Playground. MCP tool: update_watch.

POST/v1/monitors/changes

The changes your monitors found, newest first, with what was added and removed. Costs 0 checks.

{
  "limit": 5
}

{
  "changes": [],
  "credits": 0
}

curl -X POST https://api-watchmint.plxi.us/v1/monitors/changes \
  -H "X-API-Key: sk_live_..." \
  -H "Content-Type: application/json" \
  -d '{
  "limit": 5
}'

The response is the operation’s result plus credits, what the request was charged. Try it in the Playground. MCP tool: get_changes.

POST/v1/monitors/delete

Delete a monitor, with its snapshots and changes. Costs 0 checks.

{
  "monitor_id": "7c3f1a2e-5b4d-4e8f-9a6b-2d1c0e9f8a7b"
}

{
  "credits": 0,
  "deleted": true,
  "monitor_id": "7c3f1a2e-5b4d-4e8f-9a6b-2d1c0e9f8a7b"
}

curl -X POST https://api-watchmint.plxi.us/v1/monitors/delete \
  -H "X-API-Key: sk_live_..." \
  -H "Content-Type: application/json" \
  -d '{
  "monitor_id": "7c3f1a2e-5b4d-4e8f-9a6b-2d1c0e9f8a7b"
}'

The response is the operation’s result plus credits, what the request was charged. Try it in the Playground. MCP tool: stop_watching.

GET/v1/usage

Your plan and usage this billing period, for alerting before you reach the quota.

curl https://api-watchmint.plxi.us/v1/usage \
  -H "X-API-Key: sk_live_..."

{
  "plan": "starter",
  "used": 487,
  "limit": 10000,
  "period_start": "2026-07-18T09:12:44Z",
  "period_end": "2026-08-18T09:12:44Z"
}

Webhooks

Add an HTTPS endpoint under Webhooks in the dashboard, then give its id to a monitor as webhook_id. Each endpoint gets its own signing secret (whsec_…), shown once when you add it. A monitor’s webhook gets:

• monitor.changed: a check found a change, with the added and removed lines, a unified diff (up to 20,000 characters) and, for visual checks, the percent that changed and before, after and highlighted image links.
• monitor.error: the third failed check in a row (the page is down, answers with an error, or shows a bot check). The monitor is now failing and keeps being checked.
• monitor.recovered: the first good check after that.

POST /your/webhook HTTP/1.1
Content-Type: application/json
User-Agent: Watchmint-Webhooks/1
X-Watchmint-Event: monitor.changed
X-Watchmint-Event-ID: 6f1c2a7e-…:0d4e9b2c-…
X-Watchmint-Signature: sha256=3b5f0c9e41d7…

{"event": "monitor.changed", "created_at": "2026-10-31T09:00:04Z",
 "data": {"monitor": {"id": "7c3f1a2e-…", "name": "Competitor pricing", "url": "https://competitor.example/pricing", "watch": "text"},
          "check": {"status": 200, "final_url": "https://competitor.example/pricing"},
          "change": {"id": "…", "kind": "text", "summary": "1 line added, 1 removed",
                     "added": ["Pro: $59/month"], "removed": ["Pro: $49/month"],
                     "diff": "--- before\n+++ after\n@@ -3 +3 @@\n-Pro: $49/month\n+Pro: $59/month\n",
                     "visual_changed_pct": null, "images": {"before": null, "after": null, "diff": null}}}}

Every endpoint on the account also gets request.completed after each charged call, scheduled checks included, except the check whose event went to that endpoint:

{"data": {"ms": 4, "credits": 1, "endpoint": "diff.text"}, "event": "request.completed", "created_at": "2026-09-29T14:03:11.482107+00:00"}

X-Watchmint-Signature is sha256=<hex>: the HMAC-SHA256 of the raw body, keyed with the endpoint’s full secret including whsec_. Compute it over the bytes you received, before parsing:

import crypto from 'node:crypto';

// rawBody: the request body exactly as received (Buffer or string). Verify it
// before parsing -- JSON that has been parsed and re-serialised won't match.
// secret: the endpoint's full signing secret, "whsec_" prefix included.
function verifySignature(rawBody, signatureHeader, secret) {
  const expected =
    'sha256=' + crypto.createHmac('sha256', secret).update(rawBody).digest('hex');
  const given = Buffer.from(String(signatureHeader || ''));
  const want = Buffer.from(expected);
  return given.length === want.length && crypto.timingSafeEqual(given, want);
}

// Express: take this route's body raw, verify, then parse.
app.post('/your/webhook', express.raw({ type: 'application/json' }), (req, res) => {
  const ok = verifySignature(req.body, req.get('X-Watchmint-Signature'), process.env.WEBHOOK_SECRET);
  if (!ok) return res.sendStatus(401);
  const { event, data } = JSON.parse(req.body);
  res.sendStatus(200);
});