Stackbilt MCP Gateway

OAuth-authenticated Model Context Protocol (MCP) gateway for Stackbilt platform services. Built as a Cloudflare Worker using @cloudflare/workers-oauth-provider.

What It Does

A single MCP endpoint (mcp.stackbilt.dev/mcp) that routes tool calls to multiple backend product workers:

Key Features

• OAuth 2.1 with PKCE — GitHub SSO, Google SSO, and email/password authentication

• Backend adapter pattern — tool catalogs aggregated from multiple service bindings, namespaced to avoid collisions

• Security Constitution compliance — every tool declares a risk level (READ_ONLY, LOCAL_MUTATION, EXTERNAL_MUTATION); structured audit logging with secret redaction; HMAC-signed identity tokens

• Coming-soon gate — PUBLIC_SIGNUPS_ENABLED flag to control public access

• MCP JSON-RPC over HTTP — supports both streaming (SSE) and request/response transport

Quick Start

Prerequisites

• Node.js 18+

• Wrangler CLI (npm i -g wrangler)

• Cloudflare account with the required service bindings configured

Install & Run

npm install
npm run dev

Run Tests

npm test

Deploy

npm run deploy

Deploys to the mcp.stackbilt.dev custom domain via Cloudflare Workers.

Environment Variables & Secrets

Set secrets with:

wrangler secret put SERVICE_BINDING_SECRET

Project Structure

src/
  index.ts           # Entry point — OAuthProvider setup, CORS, health check bypass
  gateway.ts         # MCP JSON-RPC transport, session management, tool dispatch
  oauth-handler.ts   # OAuth 2.1 flows: login, signup, social SSO, consent
  tool-registry.ts   # Tool catalog aggregation, namespacing, schema validation
  audit.ts           # Structured audit logging, secret redaction, trace IDs
  auth.ts            # Bearer token extraction & validation
  route-table.ts     # Static routing table, tool-to-backend mapping, risk levels
  types.ts           # Type definitions, RiskLevel enum, interfaces

test/
  audit.test.ts
  auth.test.ts
  gateway.test.ts
  oauth-handler.test.ts
  route-table.test.ts
  tool-registry.test.ts

docs/
  user-guide.md      # End-user guide: account creation, client setup, tool usage
  api-reference.md   # MCP tool surface, authentication flow, tool routing
  architecture.md    # System design, security model, request flow

Test Suite

122 tests across 6 test files covering:

• OAuth handler — identity token signing/verification, login, signup, social OAuth flows, consent, HTML escaping

• Gateway — session lifecycle, initialize, tools/list, tools/call, SSE streaming, error handling

• Audit — secret redaction patterns (API keys, bearer tokens, hex hashes, password fields), trace IDs, queue emission

• Auth — bearer token extraction, API key vs JWT validation, error mapping

• Tool registry — catalog building, name mapping, schema validation, risk level enforcement

• Route table — route resolution, risk level lookup

npm test          # single run
npm run test:watch # watch mode

Documentation

• User Guide — account creation, client setup, tool usage

• API Reference — MCP tools, authentication, tool routing

• Architecture — system design, security model, data flow

License

Proprietary — Stackbilt, Inc.