Tutorial: How to use Supabase Auth in your Remote FastMCP Server

[DPLucent]

Hey!

So I’ve been messing around with FastMCP recently for some LLM tooling stuff, and one thing I ran into was that at the moment (v2.6.0) it only supports simple JWT Bearer Auth out of the box.

I wanted to use Supabase Auth instead (since it’s clean and already handling signup/login in my frontend), but there wasn’t really a drop-in integration for FastMCP. So I hacked one together and wrote a quick tutorial on how to do it.

👉 Here’s the article on Medium for the full step-by-step guide and source code.

https://medium.com/@dimi/tutorial-how-to-use-supabase-auth-with-your-fastmcp-server-6fb826573d98

🔧 TL;DR – How to hook up Supabase Auth with FastMCP:
You basically need to:

Subclass BearerAuthProvider from FastMCP

Override load_access_token(token) — that’s where you can put your own logic to perform the token validation -> note you can put any custom logic you want here! so you can extend this for other providers too, or your own logic

Inside that function, make a request to Supabase’s auth/v1/user endpoint with the token

If it’s valid, return a proper AccessToken object

If not, return None or raise TokenInvalidException

Then wire up that auth provider when you spin up your FastMCP server.

I also dropped in a sample tool to extract user info from the token using FastMCP’s get_access_token() util.

Super clean once it’s up and running — and the MCP Inspector tool makes testing it easy too. Just plug in your Supabase generated JWT and you're good.

Interested to hear what MCPs you guys are building!