MOmooreds·Jun 19, 2026
Yeah, I recently documented how to use pre-registered clients with FusionAuth[0] (my employer). DCR's newer, better sibling CIMD is on our radar and under active discussion[1], but not currently available.
An alternative to the proxy you suggest is to generate a new Entra client id (with PKCE enabled) for every MCP client in a developer portal or similar, then have the user configure their client with that client id. Here's the CLI command I found to do this[2], but I bet there's an API too. Here are config instructions for Claude Code[3] and ChatGPT[4].
Client pre-registration is acceptable, but not optimal, for developers, and is a first class citizen in the spec[5]. If your main audience is internal and you can expect them to follow configuration instructions to get access to the MCP server, this approach can work.
But it's definitely
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not acceptable for widespread, public integrations if your audience is not developers. That is where a lot of the power and opportunity for MCP lies.
0: https://fusionauth.io/docs/extend/examples/controlling-acces...
1: https://github.com/FusionAuth/fusionauth-issues/issues/3230
2: https://learn.microsoft.com/en-us/cli/azure/ad/app?view=azur...
3: https://code.claude.com/docs/en/mcp
4: https://developers.openai.com/api/docs/guides/developer-mode
5: https://modelcontextprotocol.io/specification/2025-11-25/bas...