Power Platform Community Forum Thread Details

I'm trying to connect Copilot Studio to a custom MCP Server hosted on Azure Functions using Dynamic OAuth mode. The DCR (Dynamic Client Registration) endpoints I implemented work perfectly when tested from command line, but Copilot Studio gets a 403 Forbidden error. I've exhausted my troubleshooting options and need help identifying what's different about Copilot Studio's requests.

Setup Summary:
Constraints (org policy):

❌ No client secrets allowed
❌ Cannot use "Allow requests from any application" in Easy Auth
❌ API keys not supported

What I configured:

Component	Configuration
App Registration	Single-tenant, exposed scopes, redirect URI from Copilot Studio added
Easy Auth	Microsoft provider, allowedApplications with Power Platform client IDs
Excluded Paths	/.well-known/, /register, /register/
IP Restrictions	CopilotActions, PowerPlatformInfra, PowerPlatformPlex, AzureConnectors service tags allowed
Custom DCR Endpoints	Implemented RFC 7591/8414/9728 since Entra ID doesn't support DCR natively

Copilot Studio Settings:

Auth Type: OAuth 2.0 → Dynamic
Authorization/Token URLs pointing to Entra ID

The Problem:
Error: GetDynamicClientRegistrationResultAsync failed. Status Code: Forbidden

What works (tested via curl/PowerShell):

✅ GET /.well-known/oauth-protected-resource → 200 OK
✅ GET /.well-known/oauth-authorization-server → 200 OK
✅ POST /register → 201 Created (returns client_id/secret)

What fails:

Copilot Studio gets 403 when attempting the same DCR flow.

Questions:

What client IDs / source IPs does Copilot Studio use for DCR requests in Dynamic OAuth mode?
Are there additional service tags needed beyond CopilotActions, PowerPlatformInfra, PowerPlatformPlex?
Does Copilot Studio send headers that might bypass Easy Auth's excluded paths?
Has anyone successfully used Dynamic OAuth with Azure Functions + IP restrictions + Easy Auth allowedApplications?

Any insights appreciated!

Categories:

Model context protocol

Autonomous agents

Hello,

Copilot Studio accesses MCP servers through the Power Platform connector infrastructure, meaning traffic flows via the Power Platform backend using connector networking, identity, and service infrastructure rather than the user’s browser. However, Microsoft documentation does not publish static IP ranges, client IDs, or detailed authentication specifics (such as DCR client identities), implying these requests originate from internal platform services that are not externally documented.

In practice, this creates challenges when combining Dynamic Client Registration (DCR), Azure Functions, Easy Auth, and strict IP or application restrictions. IP allowlists may block DCR requests because required backend infrastructure is not fully documented, and Easy Auth’s allowedApplications setting can cause 403 errors since the registering client identity is unknown. Additionally, Copilot Studio’s backend gateway may inject authentication headers that cause Easy Auth to treat DCR endpoints as protected resources even when excluded.
Workarounds used successfully in similar MCP and OAuth setups include separating DCR endpoints from Easy Auth (e.g., hosting registration endpoints in a dedicated function app), introducing Azure API Management or Front Door to manage authentication flow, temporarily relaxing application restrictions during registration, or replacing dynamic OAuth registration with federated identity approaches.

Overall, there is currently no publicly documented list of Copilot Studio DCR client IDs, service tags, or confirmed working examples of Dynamic OAuth with Easy Auth and strict IP restrictions, making architectural separation of DCR from protected resources the most reliable solution.