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Power Platform Community / Forums / Copilot Studio / MCP Custom Connector E...
Copilot Studio
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MCP Custom Connector Error from Example

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I am trying Pujarini Mohaptra's great post about an end-to-end scenario. I am able to get the server deployed and working in Azure per the instructions. I am able to test the SSE endpoint in a browser and get a session ID. However, when I create the custom connector and test it I get the following error: Property "" type mismatch, Expected: "object", Actual: "string".
 
 
Has anyone else run into this? 
 
Thanks!
Andrew
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  • Verified answer
    pmohapatra-msft Profile Picture
    Microsoft Employee on at
    Hi @Andrew I've added a Troubleshooting section that might be helpful.
    Feel free to check it out here: https://github.com/biswapm/calculator-sse/blob/main/README.md#️-troubleshooting. From the screenshot, it looks like the code may not have deployed correctly as an SSE endpoint.
     

    Troubleshooting

    How to Check if Your SSE Server is Running Properly

    Follow these steps to verify that your SSE (Server-Sent Events) server is functioning correctly:


    Step 1: Browse the SSE Endpoint

    • Open your browser and navigate to:

      • http://localhost:3000/sse (if running locally), or
      • Your deployed Azure URL.
    • Open Developer Tools  Network tab.

    • Look for an EventStream connection.

    • Under the Event section, you should see:

      • Endpoint: SSE endpoint
      • Data: Your Full URI endpoint

    SSE Browser Network Trace


    Step 2: Test SSE Endpoint via Postman

    1. Copy the Full URI (from the EventStream data).
    2. Use Postman to send a POST request to that URI.

    Example URL:

    http://calculatormcp-dummyurl.azurewebsites.net/mcpfy/v1/calculatordemo?sessionId=620c84e1-81e2-484d-8737-a7fbc93165b1
    
     

    Example Request Payload:

    {
      "jsonrpc": "2.0",
      "id": "2",
      "method": "tools/call",
      "params": {
        "name": "calculate-bmi",
        "arguments": {
          "weightKg": 180,
          "heightM": 1.8
        }
      }
    }
     

    If successful, you'll receive a response with a "message" confirming that the server is working correctly.


    Sample Screenshots

    Browser Network Event Trace:

    Event Trace

    Postman Response:

    Postman Output

    Alternatively, you can use MCP Inspector to test, https://github.com/modelcontextprotocol/inspector

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