Claude desktop won't invoke my tools unless I stop the response

[shmul]

Hi,

I'm facing a very weird (and frustrating) behavior of Claude desktop with an MCP server I implemented. Claude recognizes the server, tools and prompts but whenever I ask it to invoke one of the tools (including the calculator provided in the examples) it just spins forever. When I manually stop the response (using the stop button in the chat) I immediately see in the server logs that the tool is actually invoked and returns its expected output. I used mcp-inspector to verify that the server is indeed conformant, erased Claude's caches and looked into its logs but I'm unable to find a clue to this weird behavior.

Did anyone else encounter it? Any hints.

Cheers, Shmul

[shmul]

Update - while Claude Desktop still isn't able to use my MCP server, claude-code (the cli tool) flawlessly works. It also supports SSE (unlike the Desktop app).

[shmul]

Update - a security tool running on my laptop is to blame. No issue whatsoever with the code.

[rwjblue-glean]

Thanks for following up here @shmul!