Universal MCP OAuth Gateway (with Excalidraw & Proxy Support)

A deployable, serverless Universal Model Context Protocol (MCP) OAuth Gateway & Proxy built on Next.js 14.

This project allows you to attach OAuth 2.0 authentication to Excalidraw OR ANY external MCP server so enterprise clients like Google Spark & Gemini Agents can connect seamlessly without OAuth rejection errors.

---

How It Works

[Google Spark Client] ──(OAuth 2.0 Auth + Discovery)──> [Universal MCP OAuth Gateway on Vercel]
                                                                  │
                                       ┌──────────────────────────┴──────────────────────────┐
                                       ▼                                                     ▼
                     [Built-in Tools: Excalidraw, SVG, Mindmaps]      [Proxy Mode: Any External Remote MCP Server]

---

Features

• 🔐 Universal OAuth 2.0 Auth Server: Implements /.well-known/oauth-authorization-server and /.well-known/openid-configuration with RFC 7591 dynamic client registration.
• 🌐 MCP Server & Proxy Gateway:
  • Mode 1 (Built-in): Excalidraw tools (create_diagram, generate_flowchart, generate_mindmap, export_svg, view_diagram) & web utilities.
  • Mode 2 (Universal Proxy): Proxies JSON-RPC 2.0 requests to any unauthenticated remote MCP server specified via UPSTREAM_MCP_URL or X-MCP-Target-URL.
• 🖼️ Interactive Web Viewer: Embedded viewer at /view/[id] allowing users & AI agents to inspect, copy, and download rendered Excalidraw diagrams as SVG.
• ⚡ 100% Vercel Native: Uses stateless JWT tokens—no database setup required.

---

Google Spark Connection & Deployment Instructions

Step 1: Deploy to Vercel

1. Push this repository to GitHub.
2. Import the project into Vercel.
3. (Optional for Proxy Mode): If you want to proxy another unauthenticated MCP server, add an Environment Variable in Vercel:

   UPSTREAM_MCP_URL = https://your-other-mcp-server.com/api/mcp
   

4. Click Deploy. Vercel will assign a public domain, e.g.: https://your-mcp-gateway.vercel.app

Step 2: Connect to Google Spark / Gemini

1. In Google Spark, select Add Remote MCP Server.
2. Enter your deployed MCP Endpoint URL:

   https://your-mcp-gateway.vercel.app/api/mcp
   

3. Google Spark automatically discovers the OAuth endpoints at:

   https://your-mcp-gateway.vercel.app/.well-known/oauth-authorization-server
   

4. Complete the one-click authorization prompt. Google Spark can now invoke tools from Excalidraw or your proxied MCP server!

---

API Endpoints

Endpoint	Description
GET /.well-known/oauth-authorization-server	OAuth 2.0 Server Discovery Metadata (RFC 8414)
GET /.well-known/openid-configuration	OpenID Connect Discovery Metadata
POST /api/auth/register	RFC 7591 Dynamic Client Registration
GET /api/auth/authorize	OAuth Authorization endpoint
POST /api/auth/token	OAuth Token Exchange endpoint
POST /api/mcp	MCP HTTP JSON-RPC 2.0 Tool Execution / Proxy Endpoint
GET /api/mcp/sse	MCP Server-Sent Events Transport
GET /view/[id]	Interactive Excalidraw Canvas Viewer