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Auth Agent Skill

by vercel

Authentication integration guidance — Clerk (native Vercel Marketplace), Descope, and Auth0 setup for Next.js applications. Covers middleware auth patterns, sign-in/sign-up flows, and Marketplace provisioning. Use when implementing user authentication.

3k tokens
context cost
the whole folder, loaded on every use
1
files
instructions only
0
copies elsewhere
how many repositories repackaged it
240
stars on the repo
on the repository, not the skill itself

Install

one command, takes just this skill from the repository 
npx skills add https://github.com/vercel/vercel-plugin --skill auth

The instruction itself

25 sections, as written by the author

Authentication Integrations

You are an expert in authentication for Vercel-deployed applications — covering Clerk (native Vercel Marketplace integration), Descope, and Auth0.

Clerk (Recommended — Native Marketplace Integration)

Clerk is a native Vercel Marketplace integration with auto-provisioned environment variables and unified billing. Current SDK: @clerk/nextjs v7 (Core 3, March 2026).

Install via Marketplace

# Install Clerk from Vercel Marketplace (auto-provisions env vars)
vercel integration add clerk

Auto-provisioned environment variables:

  • CLERK_SECRET_KEY — server-side API key
  • NEXT_PUBLIC_CLERK_PUBLISHABLE_KEY — client-side publishable key

SDK Setup

# Install the Clerk Next.js SDK
npm install @clerk/nextjs

Middleware Configuration

// middleware.ts
import { clerkMiddleware } from "@clerk/nextjs/server";

export default clerkMiddleware();

export const config = {
  matcher: [
    // Skip Next.js internals and static files
    "/((?!_next|[^?]*\\.(?:html?|css|js(?!on)|jpe?g|webp|png|gif|svg|ttf|woff2?|ico|csv|docx?|xlsx?|zip|webmanifest)).*)",
    // Always run for API routes
    "/(api|trpc)(.*)",
  ],
};

Protect Routes

// middleware.ts — protect specific routes
import { clerkMiddleware, createRouteMatcher } from "@clerk/nextjs/server";

const isProtectedRoute = createRouteMatcher(["/dashboard(.*)", "/api(.*)"]);

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

Frontend API Proxy (Core 3)

Proxy Clerk's Frontend API through your own domain to avoid third-party requests:

// middleware.ts
export default clerkMiddleware({
  frontendApiProxy: { enabled: true },
});

Provider Setup

// app/layout.tsx
import { ClerkProvider } from "@clerk/nextjs";

export default function RootLayout({
  children,
}: {
  children: React.ReactNode;
}) {
  return (
    <ClerkProvider>
      <html lang="en">
        <body>{children}</body>
      </html>
    </ClerkProvider>
  );
}

Sign-In and Sign-Up Pages

// app/sign-in/[[...sign-in]]/page.tsx
import { SignIn } from "@clerk/nextjs";

export default function Page() {
  return <SignIn />;
}

// app/sign-up/[[...sign-up]]/page.tsx
import { SignUp } from "@clerk/nextjs";

export default function Page() {
  return <SignUp />;
}

Add routing env vars to .env.local:

NEXT_PUBLIC_CLERK_SIGN_IN_URL=/sign-in
NEXT_PUBLIC_CLERK_SIGN_UP_URL=/sign-up

Access User Data

// Server component
import { currentUser } from "@clerk/nextjs/server";

export default async function Page() {
  const user = await currentUser();
  return <p>Hello, {user?.firstName}</p>;
}

// Client component
"use client";
import { useUser } from "@clerk/nextjs";

export default function UserGreeting() {
  const { user, isLoaded } = useUser();
  if (!isLoaded) return null;
  return <p>Hello, {user?.firstName}</p>;
}

API Route Protection

// app/api/protected/route.ts
import { auth } from "@clerk/nextjs/server";

export async function GET() {
  const { userId } = await auth();
  if (!userId) {
    return Response.json({ error: "Unauthorized" }, { status: 401 });
  }
  return Response.json({ userId });
}

Descope

Descope is available on the Vercel Marketplace with native integration support.

Install via Marketplace

vercel integration add descope

SDK Setup

npm install @descope/nextjs-sdk

Provider and Middleware

// app/layout.tsx
import { AuthProvider } from "@descope/nextjs-sdk";

export default function RootLayout({
  children,
}: {
  children: React.ReactNode;
}) {
  return (
    <AuthProvider projectId={process.env.NEXT_PUBLIC_DESCOPE_PROJECT_ID!}>
      <html lang="en">
        <body>{children}</body>
      </html>
    </AuthProvider>
  );
}

// middleware.ts
import { authMiddleware } from "@descope/nextjs-sdk/server";

export default authMiddleware({
  projectId: process.env.DESCOPE_PROJECT_ID!,
  publicRoutes: ["/", "/sign-in"],
});

Sign-In Flow

"use client";
import { Descope } from "@descope/nextjs-sdk";

export default function SignInPage() {
  return <Descope flowId="sign-up-or-in" />;
}

Auth0

Auth0 provides a mature authentication platform with extensive identity provider support.

SDK Setup

npm install @auth0/nextjs-auth0

Configuration

// lib/auth0.ts
import { Auth0Client } from "@auth0/nextjs-auth0/server";

export const auth0 = new Auth0Client();

Required environment variables:

AUTH0_SECRET=<random-secret>
AUTH0_BASE_URL=http://localhost:3000
AUTH0_ISSUER_BASE_URL=https://your-tenant.auth0.com
AUTH0_CLIENT_ID=<client-id>
AUTH0_CLIENT_SECRET=<client-secret>

Middleware

// middleware.ts
import { auth0 } from "@/lib/auth0";
import { NextRequest, NextResponse } from "next/server";

export async function middleware(request: NextRequest) {
  return await auth0.middleware(request);
}

export const config = {
  matcher: [
    "/((?!_next/static|_next/image|favicon.ico|sitemap.xml|robots.txt).*)",
  ],
};

Access Session Data

// Server component
import { auth0 } from "@/lib/auth0";

export default async function Page() {
  const session = await auth0.getSession();
  return session ? (
    <p>Hello, {session.user.name}</p>
  ) : (
    <a href="/auth/login">Log in</a>
  );
}

Decision Matrix

| Need | Recommended | Why |

|------|------------|-----|

| Fastest setup on Vercel | Clerk | Native Marketplace, auto-provisioned env vars |

| Passwordless / social login flows | Descope | Visual flow builder, Marketplace native |

| Enterprise SSO / SAML / multi-tenant | Auth0 | Deep enterprise identity support |

| Pre-built UI components | Clerk | Drop-in <SignIn />, <UserButton /> |

| Vercel unified billing | Clerk or Descope | Both are native Marketplace integrations |

Clerk Core 3 Breaking Changes (March 2026)

Clerk provides an upgrade CLI that scans your codebase and applies codemods: npx @clerk/upgrade. Requires Node.js 20.9.0+.

  • auth() is async — always use const { userId } = await auth(), not synchronous
  • auth.protect() moved — use await auth.protect() directly, not from the return value of auth()
  • clerkClient() is async — use await clerkClient() in middleware handlers
  • authMiddleware() removed — migrate to clerkMiddleware()
  • @clerk/types deprecated — import types from SDK subpath exports: import type { UserResource } from '@clerk/react/types' (works from any SDK package)
  • ClerkProvider no longer forces dynamic rendering — pass the dynamic prop if needed
  • Cache components — when using Next.js cache components, place <ClerkProvider> inside <body>, not wrapping <html>
  • Satellite domains — new satelliteAutoSync option skips handshake redirects when no session cookies exist
  • Smaller bundles — React is now shared across framework SDKs (~50KB gzipped savings)
  • Better offline handling — getToken() now correctly distinguishes signed-out from offline states

Cross-References

  • Marketplace install and env var provisioning → ⤳ skill: marketplace
  • Middleware routing patterns → ⤳ skill: routing-middleware
  • Environment variable management → ⤳ skill: env-vars

Official Documentation

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How to use it

Copy the folder

Take vercel/auth from the repository into ~/.claude/skills for personal use, or into .claude/skills inside a project.

Check the name does not clash

The agent identifies a skill by the name field in its header. Two skills with the same name cannot sit side by side — one of them will be ignored.

Install what it needs

The instructions reference npm, npx. Without those the skill loads but fails at the first command.