Building Supabase-Like OAuth Authentication for MCP Servers

Summary

I am Jakob, an Engineer at Hypr MCP, where we help companies connect their internal applications to LLM-based workflows with the power of MCP servers. Join our waitlist or book a demo to learn more. In this blog post, I want to show you how and why we built an MCP Server Gateway that acts as a reverse proxy for one or more upstream MCP servers while adding support for the authorization framework provided by the MCP specification. # Introduction The Model Context Protocol (MCP) has emerged as the de-facto standard way for Large Language Models (LLMs) to interact with other systems. First released in November 2024, it gained traction very quickly which led to some rapid iterations in the months that followed. One of the most anticipated additions to the specification, which was added in March 2025, was support for authorization when offering an MCP server remotely via HTTP. The MCP authorization framework is built on top of the well-established OAuth2 authorization standard, specifically the currently in-progress draft version 2.1, additionally requiring identity providers (IdPs) to implement the Authorization Server Metadata (ASM) and Dynamic Client Registration (DCR) optional extensions. In June 2025, the specification was further revised to also require MCP servers to act as OAuth2 compatible Protected Resource Servers (PRS), another optional extension. In a nutshell, the protocol requires the client to first discover the authorization server URI by querying the PRS endpoint and the DCR and authorization endpoints by querying the authorization server’s ASM endpoint. It must then create an OAuth2 client using the DCR protocol and use that client to perform a regular OAuth2 authorization flow. # Comparing authentication providers for MCP servers This is a well-thought-through authorization framework, as, theoretically, it does not require implementers to add anything that is not part of the OAuth2 specification, while also allowing to authorize MCP clients without an...