JavaScript MCP Auth Server

JavaScript MCP Auth Server

This package shows the remote MCP auth boundary in JavaScript:

• Express HTTP server
• MCP Streamable HTTP transport at /mcp
• Protected Resource Metadata
• Bearer token middleware
• Keycloak token introspection
• audience validation
• mcp:tools scope enforcement
• protected add_numbers and server_status tools

Run

pnpm mcp-auth-server-js install
cp .env.example .env
pnpm mcp-auth-server-js demo:keycloak
pnpm mcp-auth-server-js start

For the demo, configure Keycloak with:

• client scope: mcp:tools
• MCP server confidential client: mcp-server
• demo client/user for obtaining an access token
• token audience: http://localhost:3000/mcp

Demo Scripts

pnpm mcp-auth-server-js demo:no-token
pnpm mcp-auth-server-js demo:metadata
pnpm mcp-auth-server-js demo:get-token
pnpm mcp-auth-server-js demo:call-tool
pnpm mcp-auth-server-js demo:bad-scope

The important point is the failure order:

1. no token returns 401 with WWW-Authenticate
2. metadata tells the client where auth lives
3. token introspection rejects inactive tokens
4. audience validation rejects tokens for another API
5. scope validation rejects tokens without mcp:tools