MCP made with McpSharp is not work any more

Bug Reports
1

Describe the Bug

The MCPs made by McpSharp is not work (shows no tool available) after last week updates.
Here is the demo of that project: MCPSharp/MCPSharp.Example at master · afrise/MCPSharp · GitHub

Steps to Reproduce

  1. Clone GitHub - afrise/MCPSharp: MCPSharp is a .NET library that helps you build Model Context Protocol (MCP) servers and clients - the standardized API protocol used by AI assistants and models. and install .Net 9 SDK
  2. Add mcp setting:
{
  "mcpServers": {
    "Test": {
      "command": "cmd",
      "args": [
        "/c",
        "%Your root path%\\MCPSharp\\MCPSharp.Example\\ && dotnet run"
      ]
    }
  }
}

Expected Behavior

It’s work and show ‘dynamicTool’

Operating System

Windows 10/11

Current Cursor Version (Menu → About Cursor → Copy)

Version: 1.3.4 (user setup)
VSCode Version: 1.99.3
Commit: bfb7c44bcb74430be0a6dd5edf885489879f2a20
Date: 2025-07-29T03:59:10.762Z
Electron: 34.5.1
Chromium: 132.0.6834.210
Node.js: 20.19.0
V8: 13.2.152.41-electron.0
OS: Windows_NT x64 10.0.26100

Additional Information

It was work before last month at least.
If it’s not supported for some reason, it’s acceptable but sad. I just wanna know the reason or official response of the change of MCP protocol.

Does this stop you from using Cursor

No - Cursor works, but with this issue

2

hi @Gong_Yihang and welcome to Cursor Forum.

Could you check the MCP itself what errors it shows?
Also check the Bottom Pane > Output tab > MCP Logs in dropdown.

Some users reported that compiling the script and running it from a path without spaces works.

3

It shows:

2025-07-31 17:08:53.812 [info] Connected to stdio server, fetching offerings
2025-07-31 17:08:53.821 [error] Error listing offerings: [
  {
    "code": "invalid_type",
    "expected": "array",
    "received": "undefined",
    "path": [
      "prompts"
    ],
    "message": "Required"
  }
]
4

Thank you for the update. From the screenshot it looks like there is an issue with the MCP itself.

You should check in McpSharp what is needed to fix this issue. The error message should help find the cause.

6

I see the issue, the response of {“method”:“prompts/list”,“jsonrpc”:“2.0”,“id”:6} is {“jsonrpc”:“2.0”,“id”:6,“result”:{}}. I guess cursor requires Prompt like:

图片
图片796×565 30.6 KB

But it’s missing in response, I’ve already recompiled the MCPSharp to fix that. May you guys make empty result workable for some situations? Just a suggestion.

And thanks.

1 Like
7

Does the empty result match the MCP standard?

8

No detail for that in Prompts - Model Context Protocol .

9

It looks like its required by MCP definition as the result is never empty.

2 Likes
10

Thanks, this was the issue for me.
I had tools in my MCP, working fine. Then I’ve added prompts, just empty for start.
And Cursor failed to retrieve both tools and prompts.

Logs should be more detailed. Location of MCP logs:

~/Library/Application Support/Cursor/logs/20250808T105855/window1/exthost

Error was
2025-08-08 11:18:35.701 [info] Connected to streamableHttp server, fetching offerings
2025-08-08 11:18:35.709 [error] Error listing offerings: MCP error -32601: Method not found

Strange, that same MCP server worked fine in GitHubCopilot. So it must be possible that if one capability fail Cursor should still try others.

11

I‘ve already forked McpSharp and fixed all issues I found, you can clone it and replace the original one : GitHub - kkle1994/MCPSharp: MCPSharp is a .NET library that helps you build Model Context Protocol (MCP) servers and clients - the standardized API protocol used by AI assistants and models.

1 Like
12

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