Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/hookdeck/webhook-skills/calendly-webhooksnpx skills add hookdeck/webhook-skills --skill calendly-webhooksgit clone --depth 1 https://github.com/hookdeck/webhook-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/hookdeck/webhook-skills/calendly-webhooks)<a href="https://agentmods.dev/skills/hookdeck/webhook-skills/calendly-webhooks"><img src="https://agentmods.dev/badge/skills/hookdeck/webhook-skills/calendly-webhooks.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00055 | $0.01405 |
| Opus 5 | $0.00028 | $0.00702 |
| Sonnet 5 | $0.00011 | $0.00281 |
| Haiku 4.5 | $0.00006 | $0.00140 |
Grade A, and why
calendly-webhooks scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 4d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
This is a copy
78% identical to adyen-webhooks — 160 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 123 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Calendly Webhooks
When to Use This Skill
- How do I receive Calendly webhooks?
- How do I verify Calendly webhook signatures?
- How do I handle
invitee.createdorinvitee.canceledevents? - 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:
Common Event Types
| Event | Triggered When |
|---|---|
invitee.created |
An invitee schedules an event |
invitee.canceled |
An invitee cancels a scheduled event |
invitee_no_show.created |
An invitee is marked as a no-show |
invitee_no_show.deleted |
A no-show mark is removed from an invitee |
routing_form_submission.created |
A routing form is submitted |
What ships with it
19 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
- examples/express/.env.example 201 B
- examples/express/package.json 372 B
- examples/express/README.md 1.4 KB
- examples/express/src/index.js 4.1 KB runs code
- examples/express/test/webhook.test.js 5.1 KB runs code
- examples/fastapi/.env.example 136 B
- examples/fastapi/main.py 3.4 KB runs code
- examples/fastapi/README.md 1.6 KB
- examples/fastapi/requirements.txt 82 B
- examples/fastapi/test_webhook.py 4.9 KB runs code
- examples/nextjs/.env.example 136 B
- examples/nextjs/app/webhooks/calendly/route.ts 3.2 KB runs code
- examples/nextjs/package.json 483 B
- examples/nextjs/README.md 1.4 KB
- examples/nextjs/test/webhook.test.ts 4.5 KB runs code
- examples/nextjs/vitest.config.ts 140 B runs code
- references/overview.md 2.4 KB
- references/setup.md 3.0 KB
- references/verification.md 4.9 KB
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 4d ago First seen · 123 lines · 55 tokens per session scan A 4b7bd7f8df08
calendly-webhooks is a skill published in the GitHub repository hookdeck/webhook-skills (84 stars, last pushed today), licensed MIT. It adds 55 tokens to every session and 1,405 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 78% identical to adyen-webhooks, differing in 160 lines, and is treated as a copy.
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