clerk-webhooks

clerk-webhooks is a skill for Claude Code from vvedantb/eva. It costs 53 tokens per session (3,155 once invoked), scanned A, original, MIT.

A guide for receiving and processing Clerk webhooks, which are messages sent when events such as sign-ups or organization changes happen. It covers checking that each message genuinely came from Clerk.

In plain words
What is it for?
Use it to sync Clerk data to another database, send notifications, or trigger integrations after user, session, organization, billing, or payment events.
Why use it?
Webhook delivery can be delayed or retried, so the guide helps avoid using it for actions that need an immediate result. Signature verification prevents attackers from sending fake events to the handler.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter. Also seen: installed under .agents/ (shared by several agents).

Install

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.

agentmods
npx agentmods add skills/vvedantb/eva/clerk-webhooks
Any agent
npx skills add vvedantb/eva --skill clerk-webhooks
Clone the repo
git clone --depth 1 https://github.com/vvedantb/eva

Made for: Claude Code.

Wrote 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.

agentmods badge for clerk-webhooks

README.md
[![agentmods](https://agentmods.dev/badge/skills/vvedantb/eva/clerk-webhooks.svg)](https://agentmods.dev/skills/vvedantb/eva/clerk-webhooks)
Your own site
<a href="https://agentmods.dev/skills/vvedantb/eva/clerk-webhooks"><img src="https://agentmods.dev/badge/skills/vvedantb/eva/clerk-webhooks.svg" alt="Measured on agentmods" height="20"></a>
Per session 53 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,155 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00053 $0.03155
Opus 5 $0.00026 $0.01577
Sonnet 5 $0.00011 $0.00631
Haiku 4.5 $0.00005 $0.00315

Measured 6d ago against content hash 7e5d4e3176c6, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

clerk-webhooks scanned grade A with 1 finding 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 6d 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

await fetch(process.env.SLACK_WEBHOOK_URL!, {
.agents/skills/clerk-webhooks/SKILL.md · 354 lines

How it starts

The opening of the file, as written. The whole thing — 354 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Webhooks

Output complete, working webhook handlers with verifyWebhook(req) verification in every handler.

When to Use Webhooks

Webhooks are asynchronous and eventually consistent. Delivery is fast but not guaranteed to be immediate, and may occasionally fail (Svix retries on a fixed schedule). Use them for:

  • Database sync (a separate users / orgs table that follows Clerk)
  • Notifications (welcome emails, Slack pings, internal alerts)
  • Integrations triggered by lifecycle events

Do NOT rely on webhook delivery as part of a synchronous flow such as onboarding ("user signs up, then we read X from our DB"). For data the user just created, read it from the Clerk session token or call the Backend API directly. Webhooks fill the gap when you need data about other users or events the session token doesn't carry.

Verify Every Webhook

Use verifyWebhook(req) from the framework-specific package (@clerk/nextjs/webhooks, @clerk/express/webhooks, etc.). It reads CLERK_WEBHOOK_SIGNING_SECRET automatically and throws on bad signatures. Skipping verification, even for notification-only handlers, exposes the endpoint to spoofed events.

Make the Webhook Route Public

Webhook routes must be excluded from Clerk middleware protection. Without this, Clerk returns 401.

// proxy.ts (Next.js <=15: middleware.ts)
import { clerkMiddleware, createRouteMatcher } from "@clerk/nextjs/server";

const isPublicRoute = createRouteMatcher(["/api/webhooks(.*)"]);

export default clerkMiddleware(async (auth, req) => {
  if (!isPublicRoute(req)) await auth.protect();
});

Complete Webhook Handler (Next.js App Router)

// app/api/webhooks/route.ts
import { verifyWebhook } from "@clerk/nextjs/webhooks";
import { NextRequest } from "next/server";
import { db } from "@/lib/db";

export async function POST(req: NextRequest) {
  // ALWAYS verify - never skip, even for notification-only handlers
  let evt;
  try {
    evt = await verifyWebhook(req); // uses CLERK_WEBHOOK_SIGNING_SECRET automatically
  } catch (err) {
    console.error("Webhook verification failed:", err);
    return new Response("Verification failed", { status: 400 });
  }

  if (evt.type === "user.created") {
    const { id, email_addresses, first_name, last_name } = evt.data;
    const email = email_addresses[0]?.email_address;
    const name = `${first_name ?? ""} ${last_name ?? ""}`.trim();
    await db.users.create({ data: { clerkId: id, email, name } });
  }

  if (evt.type === "user.updated") {
    const { id, email_addresses, first_name, last_name } = evt.data;
    const email = email_addresses[0]?.email_address;
    await db.users.update({
      where: { clerkId: id },
      data: { email, first_name, last_name },
    });
  }

  if (evt.type === "user.deleted") {
    const { id } = evt.data;
    await db.users.delete({ where: { clerkId: id } });
  }

  if (evt.type === "organizationMembership.created") {
    const { organization, public_user_data, role } = evt.data;
    const orgId = organization.id;
    const userId = public_user_data.user_id;
    await db.teamMembers.create({ data: { orgId, userId, role } });
  }

  if (evt.type === "organizationMembership.deleted") {
    const { organization, public_user_data } = evt.data;
    const orgId = organization.id;
    const userId = public_user_data.user_id;
    await db.teamMembers.delete({ where: { orgId_userId: { orgId, userId } } });
  }

  return new Response("OK", { status: 200 });
}

Read the full file on GitHub · 354 lines

Files

What ships with it

2 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.

Changes

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.

  1. 6d ago First seen · 354 lines · 53 tokens per session scan A 7e5d4e3176c6

Subscribe to this mod's changes

clerk-webhooks is a skill published in the GitHub repository vvedantb/eva (101 stars, last pushed yesterday), licensed MIT. It adds 53 tokens to every session and 3,155 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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