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Plugins extend xmcp’s functionality by adding authentication, monetization, and payment capabilities to your MCP servers. Each plugin integrates seamlessly with xmcp’s middleware system.

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What are Plugins?

xmcp plugins are middleware providers that add functionality to your MCP server. They:
  • Integrate with external services (Auth0, Clerk, WorkOS, Polar, etc.)
  • Handle authentication and authorization
  • Enable monetization and payment flows
  • Provide type-safe context to your tools
  • Expose OAuth metadata endpoints for MCP clients

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Available Plugins

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Authentication Plugins

Authentication plugins add user identity and access control to your MCP server:

Auth0

Enterprise authentication with OAuth 2.0, scopes, and permissions

Clerk

Modern authentication with organizations and role-based access

Better Auth

Self-hosted authentication with email/password and OAuth providers

WorkOS

Enterprise-ready authentication with AuthKit and SSO

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Monetization Plugins

Monetization plugins enable payment and licensing models:

Polar

License key validation and usage-based billing with meter credits

x402

Pay-per-use pricing with cryptocurrency payments (USDC)

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Plugin Architecture

All authentication plugins follow a consistent pattern:

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1. Provider Setup

Create a middleware.ts file in your xmcp app: 
import { auth0Provider } from "@xmcp-dev/auth0";

export default auth0Provider({
  domain: process.env.DOMAIN!,
  audience: process.env.AUDIENCE!,
  baseURL: process.env.BASE_URL!,
  clientId: process.env.CLIENT_ID!,
  clientSecret: process.env.CLIENT_SECRET!,
});

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2. OAuth Metadata

Authentication plugins automatically expose:
  • GET /.well-known/oauth-protected-resource - Resource metadata
  • GET /.well-known/oauth-authorization-server - Authorization server metadata
MCP clients use these endpoints for Dynamic Client Registration (DCR).

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3. Context Access

Access authenticated user data in your tools: 
import { getAuthInfo } from "@xmcp-dev/auth0";

export default function myTool() {
  const authInfo = getAuthInfo();
  return `Hello, ${authInfo.user.name}!`;
}

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Choosing a Plugin

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Authentication

Use Auth0 when you need:
  • Enterprise-grade authentication
  • Fine-grained permissions system
  • M2M (machine-to-machine) authentication
  • Resource Server scopes
Use Clerk when you need:
  • Quick setup with minimal configuration
  • Organizations with roles and permissions
  • Beautiful pre-built UI components
  • Modern developer experience
Use Better Auth when you need:
  • Self-hosted authentication
  • Full control over your data
  • PostgreSQL-based session management
  • Custom authentication flows
Use WorkOS when you need:
  • Enterprise SSO (SAML, OIDC)
  • Directory sync (SCIM)
  • Magic link authentication
  • Multi-tenant applications

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Monetization

Use Polar when you need:
  • License key management
  • Usage-based billing with meters
  • Subscription models
  • Checkout integration
Use x402 when you need:
  • Pay-per-call pricing
  • Cryptocurrency payments (USDC)
  • Instant settlement
  • No subscription management

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Installation

Install any plugin via npm: 
npm install @xmcp-dev/auth0
npm install @xmcp-dev/clerk
npm install @xmcp-dev/better-auth
npm install @xmcp-dev/workos
npm install @xmcp-dev/polar
npm install @xmcp-dev/x402

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Next Steps

Explore individual plugin documentation:

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