Calendly Webhooks Skill

When to Use This Skill

• How do I receive Calendly webhooks?
• How do I verify Calendly webhook signatures?
• How do I handle invitee.created or invitee.canceled events?
• Why is my Calendly webhook signature verification failing?
• Setting up Calendly webhook handlers and debugging replay protection

Verification (core)

Calendly signs each webhook with the Calendly-Webhook-Signature header, which contains a timestamp and a signature: t=<timestamp>,v1=<signature>. Compute HMAC-SHA256 (hex) over {timestamp}.{raw body} using the subscription's signing key, compare timing-safe, and reject stale timestamps (~3 min) to prevent replay. Calendly has no SDK verification helper — verify manually and always use the raw request body (don't JSON.parse first).

const crypto = require('crypto');

function verifyCalendlySignature(rawBody, header, signingKey, toleranceSec = 180) {
  const parts = Object.fromEntries(header.split(',').map((p) => p.split('=')));
  const timestamp = parts.t;
  const signature = parts.v1;
  if (!timestamp || !signature) return false;

  // Reject stale timestamps to prevent replay attacks
  if (Math.abs(Math.floor(Date.now() / 1000) - Number(timestamp)) > toleranceSec) return false;

  const expected = crypto
    .createHmac('sha256', signingKey)
    .update(`${timestamp}.${rawBody}`) // signed content = timestamp + "." + raw body
    .digest('hex');

  try {
    return crypto.timingSafeEqual(Buffer.from(signature, 'hex'), Buffer.from(expected, 'hex'));
  } catch {
    return false; // length mismatch = invalid
  }
}

For complete handlers with route wiring, event dispatch, and tests, see:

• examples/express/
• examples/nextjs/
• examples/fastapi/

Common Event Types

For the full event reference, see references/overview.md and Calendly's webhook documentation.

Environment Variables

# Signing key returned when you create the webhook subscription
CALENDLY_WEBHOOK_SIGNING_KEY=your_webhook_signing_key_here

Local Development

# Start tunnel (no account needed)
npx hookdeck-cli listen 3000 calendly --path /webhooks/calendly

Reference Materials

• references/overview.md - What Calendly webhooks are, common events
• references/setup.md - Creating a webhook subscription, getting the signing key
• references/verification.md - Signature verification details and gotchas