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 skills add cwinvestments/memstack --skill webhook-designergit clone --depth 1 https://github.com/cwinvestments/memstackWrote 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/cwinvestments/memstack/webhook-designer)<a href="https://agentmods.dev/skills/cwinvestments/memstack/webhook-designer"><img src="https://agentmods.dev/badge/skills/cwinvestments/memstack/webhook-designer/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/cwinvestments/memstack/webhook-designer"><img src="https://agentmods.dev/badge/skills/cwinvestments/memstack/webhook-designer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 5.1 | $0.00074 | $0.02557 |
| Opus 5.5 | $0.00030 | $0.01023 |
| Sonnet 5.5 | $0.00015 | $0.00511 |
| Haiku 4.5 | $0.00007 | $0.00256 |
Grade A, and why
memstack-automation-webhook-designer 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 1mo 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.
How it starts
The opening of the file, as written. The whole thing — 333 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Webhook Designer: Designing webhook handler...
Creates secure webhook handlers with endpoint design, payload validation, HMAC signature verification, retry logic, idempotency, logging, and dead letter queues.
Activation
When this skill activates, output:
Webhook Designer: Designing webhook handler...
Then execute the protocol below.
Context Guard
| Context | Status |
|---|---|
| User says "webhook", "webhook handler", "webhook endpoint" | ACTIVE |
| User says "receive events", "HMAC verification", "idempotency" | ACTIVE |
| User wants to build an endpoint that receives external events | ACTIVE |
| User wants a full n8n automation workflow | DORMANT: use n8n Workflow Builder |
| User wants a scheduled/cron job | DORMANT: use Cron Scheduler |
Common Mistakes
| Mistake | Why It's Wrong |
|---|---|
| "Skip signature verification" | Without HMAC, anyone can send fake events to your endpoint. Always verify. |
| "Process synchronously" | Long processing blocks the response. Return 200 immediately, process async. |
| "No idempotency" | Senders retry on timeout. Without idempotency keys, you'll process duplicates. |
| "Ignore retry headers" | Senders include retry count and delivery ID. Log them for debugging. |
| "Return detailed errors" | Never expose internals. Return 200 (accepted) or 400 (bad request), nothing more. |
Protocol
Step 1: Gather Webhook Requirements
If the user hasn't provided details, ask:
- Source: what service sends the webhook? (Stripe, GitHub, Shopify, custom)
- Events: which events do you need to handle? (e.g., payment.completed, push)
- Payload: what does the payload look like? (JSON schema or example)
- Auth: how does the source authenticate? (HMAC, bearer token, IP whitelist)
- Processing: what should happen when an event arrives?
- Framework: what's your stack? (Next.js, Express, FastAPI, etc.)
Step 2: Design Endpoint
Endpoint pattern:
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.
- 1mo ago Changed 75a6245b8647
- 1mo ago First seen · 333 lines · 74 tokens per session scan A 6a2a7741fe99
memstack-automation-webhook-designer is a skill published in the GitHub repository cwinvestments/memstack (425 stars, last pushed today), licensed MIT. It adds 74 tokens to every session and 2,557 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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