Does this need to be enabled as a preview feature somewhere?

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Posted on by GF-09040609-0 Microsoft Employee

Hi,

I've followed all the instructions:

- have ensured my messages api in the initial SSE response is a fully qualified URI

I have confirmed my SSE server works elsewhere (Github CoPilot).

But I cannot make it work in CoPilot Studio (tried in environments in Australia and United States).

I can see an initial request made from the custom connector to my sse endpoint, followed by a message post to Initialize the MCP connection, but it is followed pretty quickly by

Sorry, something went wrong. Error code: SystemError. Conversation ID: ******. Time (UTC): 4/9/2025 6:14:28 AM.

Really looking forwards to getting this working, and any help you can offer.

Thanks,

Graeme

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Model context protocol

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zankard Moderator on at

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Hi Graeme,

Thanks for reaching out! A couple questions for you:

1) Are you using a preview environment in Copilot Studio?

2) What language did you use to create your MCP Server?

Please feel free to reach out to me directly to share your conversation ID. We'll continue to update this thread with the resolution for others in the community.

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GF-09040609-0 Microsoft Employee on at

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@zankard thanks for replying.

How can I tell if I'm using a preview environment? I've tried a few now - but I never see an option for a 'preview' environment.

Developer, Sandbox, Trial, Production appear, and some offer a checkbox to get 'Early features'.

I know my MCP server is 100% fine as it works with other MCP clients such as Github CoPilot.

I also know the MCP server is half working with CoPilot Studio, as I see two requests to it.

- the first is to the /sse endpoint

- the second is to my (fully qualified URI) /messages endpoint

Here's the POST to the /messages endpoint from CoPilot Studio to my MCP server:

{ "jsonrpc": "2.0", "id": "1", "method": "initialize", "params": { "capabilities": {}, "clientInfo": { "name": "mcs", "version": "1.0.0" }, "protocolVersion": "2024-11-05", "sessionContext": {} } }

The response (down the /sse) stream from my MCP server is this:

data: {"jsonrpc":"2.0","id":"1","result":{"protocolVersion":"2024-11-05","capabilities":{"tools":{"listChanged":false}},"serverInfo":{"name":"Azure Functions MCP server.","version":"1.0.0.0"}}}

But CoPilot studio never follows with another request.

An example of a fail from the chat window:

Sorry, something went wrong. Error code: SystemError. Conversation ID: c734e14c-2706-42c9-bf29-48f74ed0ea8d. Time (UTC): 4/10/2025 1:50:06 AM

Hope this helps,

Graeme

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swagatm on at

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Hi Graeme,
Thanks for posting the conversation details!
If possible, can you reach out to me as I would like to debug the issue with you.
Looking at the details for the conversation you pasted below, copilot studio sends the second request to your /messages endpoint below and gets an erroneous payload from your server and hence results in the failure in chat window.
I would like to investigate this further with you. Can you please reach out to me on Teams to investigate this further.
Thanks,
Swagat

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