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/faundit-webhooksnpx skills add hookdeck/webhook-skills --skill faundit-webhooksgit clone --depth 1 https://github.com/hookdeck/webhook-skillsWhat 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 | $0.00053 | $0.01537 |
| Opus 5 | $0.00026 | $0.00768 |
| Sonnet 5 | $0.00011 | $0.00307 |
| Haiku 4.5 | $0.00005 | $0.00154 |
Grade A, and why
faundit-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 3d 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
80% identical to adyen-webhooks — 170 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 — 133 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Faundit Webhooks
When to Use This Skill
- Setting up Faundit webhook handlers
- Debugging Faundit signature verification failures
- Understanding Faundit event types (
item-status,request-status) and payloads - Handling lost-and-found item and request status changes (delivered, finished, expired, etc.)
Verification (core)
Faundit signs each webhook with HMAC-SHA256 (hex) and delivers two headers you care about:
X-Faundit-Signature-Next— current (v1) scheme, signsv1:<timestamp>:<body>(payload integrity). Prefer this.X-Faundit-Timestamp— the timestamp used in the signed string.X-Faundit-Signature— deprecated (v0) scheme, signsv0:<timestamp>only (no body integrity). Avoid.
There is no official Faundit SDK — verify manually. Use the raw request body (before JSON.parse), and build the signed string as v1: + the X-Faundit-Timestamp value + : + raw body.
const crypto = require('crypto');
// Verify the current v1 signature (X-Faundit-Signature-Next)
function verifyFaunditWebhook(rawBody, timestamp, signatureNext, secret) {
if (!signatureNext || !timestamp) return false;
const signedContent = `v1:${timestamp}:${rawBody}`; // rawBody = unparsed request body
const expected = crypto
.createHmac('sha256', secret)
.update(signedContent)
.digest('hex');
try {
return crypto.timingSafeEqual(
Buffer.from(signatureNext, '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
Faundit sends only two event types. The event-type field names the event; the granular status is the data.status field (not a separate event).
event-type |
Triggered when | data.status values |
|---|---|---|
item-status |
A found/lost item changes status | contact-missing, waiting-response, wrong-owner, pickup-by-guest, left-behind, finished, shipment-paid, pickup-scheduled, in-route, delivered, deleted, expired, anonymized |
request-status |
A lost-item request changes status | registered, not-found, resolved, deleted, expired, anonymized |
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 134 B
- examples/express/package.json 370 B
- examples/express/README.md 1.5 KB
- examples/express/src/index.js 5.0 KB runs code
- examples/express/test/webhook.test.js 4.9 KB runs code
- examples/fastapi/.env.example 134 B
- examples/fastapi/main.py 4.1 KB runs code
- examples/fastapi/README.md 1.7 KB
- examples/fastapi/requirements.txt 82 B
- examples/fastapi/test_webhook.py 5.4 KB runs code
- examples/nextjs/.env.example 134 B
- examples/nextjs/app/webhooks/faundit/route.ts 4.0 KB runs code
- examples/nextjs/package.json 482 B
- examples/nextjs/README.md 1.6 KB
- examples/nextjs/test/webhook.test.ts 4.1 KB runs code
- examples/nextjs/vitest.config.ts 140 B runs code
- references/overview.md 3.3 KB
- references/setup.md 2.0 KB
- references/verification.md 4.4 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.
- 3d ago First seen · 133 lines · 53 tokens per session scan A 17670b4febd2
faundit-webhooks is a skill published in the GitHub repository hookdeck/webhook-skills (84 stars, last pushed 6d ago), licensed MIT. It adds 53 tokens to every session and 1,537 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 80% identical to adyen-webhooks, differing in 170 lines, and is treated as a copy.
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