MCP Server known issue with SSE

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Posted on by donniekerr

https://learn.microsoft.com/en-us/microsoft-copilot-studio/agent-extend-action-mcp#known-issues--planned-improvements

What is the status of the SSE full uri response known issue? Are there any workarounds?

I have a custom MCP Server that works great with OpenAI Agents and inside the MCP Inspector. It connects with the /SSE . But it times out when trying to call it inside of an Action using my custom connector.

ChatGPT thinks /sse is responding with a relative /message url and that might be why it is timing out in copilot, but I have no evidence of that.

My working MCP Server code is super simple and when deployed to an Azure Container App it works fine in the MCP Inspector. I don't see a way to override the url in the FastMCP or mcp[cli] package, which automatically generates the responses under the hood of the /SSE request response.

import time
import datetime
import requests
from mcp.server.fastmcp import FastMCP
mcp = FastMCP("Echo Server")
@mcp.tool()
def get_current_weather(city: str) -> str:
print(f"[debug-server] get_current_weather({city})")
response = requests.get(f"https://wttr.in/{city}")
return response.text

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Model context protocol

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zankard Moderator on at

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Hi @donniekerr -

please ensure your endpoint returned in the open SSE connection call is a fully qualified URL.

For example:
By default, most standard SDK configurations return something like this:
event: endpoint
data: /message
But, Copilot Studio requires a fully qualified URI:
event: endpoint
data: https://microsoft.com/mcp/message [microsoft.com]

We are currently working on a resolution which will be available soon.

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donniekerr 59 on at

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Thank you for confirming the problem. Do you have an ETA of fix? Or is there a workaround suggestion?

Question. What is the Code tab on the Custom Connector? It says you can transform a response. Might it be possible to add the full path there before it gets to the agent?

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donniekerr 59 on at

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Any ETA on fixing this issue? Any workarounds?

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donniekerr 59 on at

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I can see in Microsoft's MCP Lab how they had to do this to get it to work with Copilot

app.get("/sse", async (req: Request, res: Response) => {
// Get the full URI from the request
const host = req.get("host");

const fullUri = `https://${host}/jokes`;
const transport = new SSEServerTransport(fullUri, res);

transports[transport.sessionId] = transport;
res.on("close", () => {
delete transports[transport.sessionId];
});
await server.connect(transport);
});

But, FastMCP in Python, I don't really see how to get this basic MCP Server working over SSE. This is the entire server that works in the inspector and by connecting to OpenAI Agents, just not copilot due to the full url requirement.

import time

import datetime

import requests

from mcp.server.fastmcp import FastMCP

mcp = FastMCP("Echo Server")

@mcp.tool()

def add(a: int, b: int) -> int:

print(f"[debug-server] add({a}, {b})")

return a + b

@mcp.tool()

def get_current_weather(city: str) -> str:

print(f"[debug-server] get_current_weather({city})")

response = requests.get(f"https://wttr.in/{city}")

return response.text

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donniekerr 59 on at

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Switching the Streamable HTTP works in a custom copilot studio connector. This solutions is fine since SSE appears to be on its way out. Marking this as the answer since I never got a response about fixing the SSE bug.

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