# MCP Server built in Cursor won't run with Claude Desktop

**URL:** <https://forum.cursor.com/t/mcp-server-built-in-cursor-wont-run-with-claude-desktop/78885>\
**Category:** Help\
**Created:** [April 14, 2025, 6:39am UTC](https://forum.cursor.com/t/mcp-server-built-in-cursor-wont-run-with-claude-desktop/78885 "2025-04-14T06:39:43Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![alexsimsy](https://sea3.discourse-cdn.com/cursor1/user_avatar/forum.cursor.com/alexsimsy/32/46813_2.png) [@alexsimsy](https://forum.cursor.com/u/alexsimsy)\
**Post date:** [April 14, 2025, 6:39am UTC](https://forum.cursor.com/t/mcp-server-built-in-cursor-wont-run-with-claude-desktop/78885/1 "2025-04-14T06:39:43Z")

</div>

I have built my own MCP server using Cursor and it works with Cursor but I am unable to get Claude Desktop to run it. I get the error “Could not attach to MCP simsy-py-mcp”. I have been unable to fix the issue and I am using Claude Desktop as the benchmark that others will be able to install and use my MCP once ready.

I have used the MCP python sdk and worked through the debugging guide and I am stuck so would appreciate any assistance.

The Claude log file shows this;  
2025-04-14T06:35:44.148Z [simsy-mcp] [info] Initializing server…  
2025-04-14T06:35:44.169Z [simsy-mcp] [info] Server started and connected successfully  
2025-04-14T06:35:44.171Z [simsy-mcp] [info] Message from client: {“method”:“initialize”,“params”:{“protocolVersion”:“2024-11-05”,“capabilities”:{},“clientInfo”:{“name”:“claude-ai”,“version”:“0.1.0”}},“jsonrpc”:“2.0”,“id”:0}  
Server failed to start - check logs/server.log for details  
Cleaning up…  
2025-04-14T06:35:54.488Z [simsy-mcp] [info] Server transport closed  
2025-04-14T06:35:54.488Z [simsy-mcp] [info] Client transport closed  
2025-04-14T06:35:54.489Z [simsy-mcp] [info] Server transport closed unexpectedly, this is likely due to the process exiting early. If you are developing this MCP server you can add output to stderr (i.e. `console.error('...')` in JavaScript, `print('...', file=sys.stderr)` in python) and it will appear in this log.  
2025-04-14T06:35:54.489Z [simsy-mcp] [error] Server disconnected. For troubleshooting guidance, please visit our [debugging documentation](https://modelcontextprotocol.io/docs/tools/debugging) {“context”:“connection”}  
2025-04-14T06:35:54.490Z [simsy-mcp] [info] Client transport closed

---

<div class="post-metadata">

**Author:** ![sdmat](https://avatars.discourse-cdn.com/v4/letter/s/7ea924/32.png) [@sdmat](https://forum.cursor.com/u/sdmat)\
**Post date:** [April 15, 2025, 6:14am UTC](https://forum.cursor.com/t/mcp-server-built-in-cursor-wont-run-with-claude-desktop/78885/2 "2025-04-15T06:14:25Z")

</div>

From the Claude log that your server is exiting for some reason, probably on initialization.

Look at logs/server.log as suggested, if there is nothing there you will need to set up your MCP server to direct debug logs to a file somewhere. That will let you troubleshoot it.

---

<div class="post-metadata">

**Author:** ![system](https://sea3.discourse-cdn.com/cursor1/user_avatar/forum.cursor.com/system/32/99069_2.png) [@system](https://forum.cursor.com/u/system)\
**Post date:** [May 15, 2025, 6:15am UTC](https://forum.cursor.com/t/mcp-server-built-in-cursor-wont-run-with-claude-desktop/78885/3 "2025-05-15T06:15:13Z")

</div>

This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.