Mcp Gate

mcp-gate

[](https://github.com/c-premus/mcp-gate/actions/workflows/ci.yaml) [](https://go.dev/) [](LICENSE)

OAuth 2.1 reverse proxy for MCP servers. Implements RFC 9728 Protected Resource Metadata and JWT validation, delegating authentication to an external authorization server.

Read the blog post: I couldn't find an OAuth 2.1 proxy for MCP servers, so I built one

What it does

mcp-gate sits in front of any MCP server and adds the MCP Authorization specification (2025-11-25) endpoints required by Claude.ai custom connectors:

1. /.well-known/oauth-protected-resource — Serves RFC 9728 metadata pointing clients to the authorization server
2. /healthz — Health check for container orchestration
3. /* — Validates Bearer JWT tokens via JWKS, then reverse-proxies to the upstream MCP server

Every request is logged as structured JSON (method, path, status, duration_ms, client_ip, user_agent) for Loki/Alloy ingestion.

Architecture

Claude.ai → Reverse Proxy → mcp-gate (JWT validation) → MCP Server → Backend
                                 ↕
                         Authorization Server (OAuth 2.1 / OIDC)

Quick Start

export LISTEN_ADDR=0.0.0.0:8080
export UPSTREAM_URL=http://mcp-server:8000
export RESOURCE_URI=https://mcp.example.com
export AUTHORIZATION_SERVER=https://auth.example.com/application/o/mcp/
export JWKS_URI=https://auth.example.com/application/o/mcp/jwks/
export EXPECTED_ISSUER=https://auth.example.com/application/o/mcp/
export EXPECTED_AUDIENCE=your-client-id

go run ./cmd/mcp-gate

Docker

docker pull cpremus/mcp-gate:latest

Images are published to Docker Hub and GHCR on each release. Available tags: latest, version (e.g. v1.2.0).

Setup

See the Setup Guide for step-by-step instructions on:

1. Creating an OAuth client in your OIDC provider (Keycloak, Authentik, Okta, Auth0, etc.)
2. Configuring mcp-gate
3. Connecting Claude.ai to the protected MCP server

Configuration

All configuration is via environment variables. See the Setup Guide for the full list.

Horizontal scaling

mcp-gate validates JWTs statelessly and is safe to run as multiple replicas behind a load balancer. The per-IP rate limiter defaults to in-memory state, which means the configured RPS holds per replica. Set REDIS_ADDR=host:port to back the limiter with Redis so the configured RPS is enforced globally across replicas. REDIS_USERNAME, REDIS_PASSWORD, and REDIS_DB are read separately so Vault can inject a password as a single secret. Redis errors fail open (the request passes through and a counter is incremented) so a Redis hiccup never blackholes user traffic.

License

MIT

Source & license

This open-source MCP server is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: c-premus
• Source: c-premus/mcp-gate
• License: MIT

Install and usage instructions live in the source repository linked above.