Claude Desktop Not Able To Detect The Tool

[ohmpatel1997]

I have created a basic MCP server using Go SDK as given in the example, updated the configuration file of claude_desktop_config.json file as per below:

{
  "mcpServers": {
    "cars": {
      "command": "/Users/ohmpatel/c-mcp-servers/showroomv2/showroom",
      "env": {}
    }
  },
  "isUsingBuiltInNodeForMcp": false
}

but claude can not show detect the tool in conversation panel:

Below is what i do:

func main() {
	server := mcp.NewServer(&mcp.Implementation{Name: "showroom", Version: "v1.0.0"}, nil)

	mcp.AddTool(server, &mcp.Tool{
		Name:        "list-showroom-cars",
		Description: "Retrieves a list of cars from the showroom with optional filtering by limit, currency, state, and offset."},
		getshowroomcars)
     
     // Run the server over stdin/stdout, until the client disconnects
	if err := server.Run(context.Background(), mcp.NewStdioTransport()); err != nil {
		log.Fatal(err)
	}

}
func getshowroomcars(ctx context.Context, session *mcp.ServerSession, req *mcp.CallToolParamsFor[any]) (*mcp.CallToolResultFor[mcp.Content], error) {
	return &mcp.CallToolResultFor[mcp.Content]{StructuredContent: &mcp.TextContent{
		Text: "welcome to example mcp tool",
	}}, nil
}

[jba]

You should upgrade to v0.3.0. Perhaps we fixed whatever bug this is.

You don't need to specify the input schema when you use mcp.AddTool. It will infer it from the argument to getshowroomcars.

I think there is some confusion over Content vs. StructuredContent. Here is an example of a v0.3.0 tool handler: https://github.com/modelcontextprotocol/go-sdk/blob/v0.3.1/examples/server/basic/main.go#L19.

See if those changes don't help. If it still doesn't work, can you send us any logs from claude? It is hard to debug without some sort of error message.

[findleyr]

We'd love to help debug this, if it is indeed still a problem. However, we need more information. Please let us know if this doesn't work with the latest version. An easy test is to run one of the examples in the examples/server directory.

[rebaz94]

I’m experiencing the same problem, but most of the time it seems to be an issue with Claude. simply restarting usually fixes it.

Currently, I’ve noticed two issues:

• I’m not sure if this is related to Claude or not, but when adding new tools, they don’t appear until after a restart, even though the mcp inspector shows that a notification was received.
• Sometimes, listing tools fails if there are tool calls during session initialization. I think the server should block until initialization is complete before allowing other requests.

[findleyr]

Thanks @rebaz94. It sounds like the initialization race might be related.

I thought we decided to block during initialization in #26. I will investigate and try to reproduce.
If you have a log of messages, that would be very helpful.

[rebaz94]

@findleyr yea, that might be the reason.

I just ran a test and saw this in the logs:

method "tools/call" is invalid during session initialization

Here’s a video I recorded, I noticed some strange behavior. The tools show up correctly the first time, but after opening Claude a second time, the tools disappear.

Hopefully, this helps :)

bug.mp4

One more thing, I’m not sure if this is already possible, but it would be great to have a way to configure the request timeout. The current timeout is so short that it often cancels the request.

logs

2025-09-03T19:02:53.565Z [rebe] [info] Message from server: {"jsonrpc":"2.0","id":3,"error":{"code":0,"message":"method \"resources/list\" is invalid during session initialization"}} { metadata: undefined }
[45841] [Remote→Local] 2
2025-09-03T19:02:53.567Z [rebe] [info] Message from server: {"jsonrpc":"2.0","id":2,"error":{"code":0,"message":"method \"prompts/list\" is invalid during session initialization"}} { metadata: undefined }
[45841] [Remote→Local] notifications/tools/list_changed
[45819] [Remote→Local] notifications/tools/list_changed
2025-09-03T19:02:57.491Z [rebe] [info] Message from server: {"jsonrpc":"2.0","method":"notifications/tools/list_changed","params":{}} { metadata: undefined }
2025-09-03T19:02:57.491Z [rebe] [info] Message from server: {"jsonrpc":"2.0","method":"notifications/tools/list_changed","params":{}} { metadata: undefined }
[45841] [Remote→Local] notifications/tools/list_changed
[45819] [Remote→Local] notifications/tools/list_changed
2025-09-03T19:02:58.093Z [rebe] [info] Message from server: {"jsonrpc":"2.0","method":"notifications/tools/list_changed","params":{}} { metadata: undefined }
2025-09-03T19:02:58.094Z [rebe] [info] Message from server: {"jsonrpc":"2.0","method":"notifications/tools/list_changed","params":{}} { metadata: undefined }
2025-09-03T19:02:58.448Z [rebe] [info] Message from client: {"jsonrpc":"2.0","method":"notifications/cancelled","params":{"requestId":1,"reason":"McpError: MCP error -32001: Request timed out"}} { metadata: undefined }
[45819] [Local→Remote] notifications/cancelled
2025-09-03T19:02:58.558Z [rebe] [info] Message from client: {"jsonrpc":"2.0","method":"notifications/cancelled","params":{"requestId":1,"reason":"McpError: MCP error -32001: Request timed out"}} { metadata: undefined }
[45841] [Local→Remote] notifications/cancelled

[findleyr]

@rebaz94 which transport are you using for the server?

It looks like the initialize request is timing out. Are there any earlier logs?

[findleyr]

Regarding the request timeout: that's a client-side setting. I'm not sure how it is configured.

[rebaz94]

StreamableHttpTransport is being used.

Are there any earlier logs?

No, this is from the very beginning.

[findleyr]

Thanks. The reason I ask is because of this log:

2025-09-03T19:02:58.448Z [rebe] [info] Message from client: {"jsonrpc":"2.0","method":"notifications/cancelled","params":{"requestId":1,"reason":"McpError: MCP error -32001: Request timed out"}} { metadata: undefined }
[45819] [Local→Remote] notifications/cancelled

The client is cancelling request 1, but the logs don't indicate that there is a request 1. Similarly, the go-sdk logs indicate that it is waiting for initialize (which would be request 1). I wonder if this is a claude bug. I will have to try to reproduce tomorrow.

[rebaz94]

I may have trimmed the log earlier, sorry.

Here’s another one:

47136] Using automatically selected callback port: 44196
[47136] [47136] Connecting to remote server: http://localhost:8081/mcp
[47136] Using transport strategy: http-first
[47152] Using automatically selected callback port: 44196
[47152] [47152] Connecting to remote server: http://localhost:8081/mcp
[47152] Using transport strategy: http-first
[47136] Connected to remote server using StreamableHTTPClientTransport
[47136] Local STDIO server running
[47136] Proxy established successfully between local STDIO and remote StreamableHTTPClientTransport
[47136] Press Ctrl+C to exit
[47136] [Local→Remote] initialize
[47136] {
  "jsonrpc": "2.0",
  "id": 0,
  "method": "initialize",
  "params": {
    "protocolVersion": "2025-06-18",
    "capabilities": {},
    "clientInfo": {
      "name": "claude-ai (via mcp-remote 0.1.29)",
      "version": "0.1.0"
    }
  }
}
[47136] [Remote→Local] 0
2025-09-03T19:09:54.849Z [rebe] [info] Message from server: {"jsonrpc":"2.0","id":0,"result":{"capabilities":{"logging":{},"tools":{"listChanged":true}},"instructions":"1.0","protocolVersion":"2025-06-18","serverInfo":{"name":"my-server","title":"My Server","version":"1.0"}}} { metadata: undefined }
2025-09-03T19:09:54.850Z [rebe] [info] Message from client: {"method":"notifications/initialized","jsonrpc":"2.0"} { metadata: undefined }
2025-09-03T19:09:54.850Z [rebe] [info] Message from client: {"method":"tools/list","params":{},"jsonrpc":"2.0","id":1} { metadata: undefined }
2025-09-03T19:09:54.850Z [rebe] [info] Message from client: {"method":"prompts/list","params":{},"jsonrpc":"2.0","id":2} { metadata: undefined }
2025-09-03T19:09:54.850Z [rebe] [info] Message from client: {"method":"resources/list","params":{},"jsonrpc":"2.0","id":3} { metadata: undefined }
[47136] [Local→Remote] notifications/initialized
[47136] [Local→Remote] tools/list
[47136] [Local→Remote] prompts/list
[47136] [Local→Remote] resources/list
[47136] Error from remote server: TypeError: Cannot read properties of undefined (reading 'tools')
    at transformResponseFunction (file:///Users/rebo/.npm/_npx/1a3c4333f3a90708/node_modules/mcp-remote/dist/chunk-AKJME7CQ.js:13738:31)
    at Object.interceptResponse (file:///Users/rebo/.npm/_npx/1a3c4333f3a90708/node_modules/mcp-remote/dist/chunk-AKJME7CQ.js:13699:39)
    at transportToServer.onmessage (file:///Users/rebo/.npm/_npx/1a3c4333f3a90708/node_modules/mcp-remote/dist/chunk-AKJME7CQ.js:13765:40)
    at processStream (file:///Users/rebo/.npm/_npx/1a3c4333f3a90708/node_modules/mcp-remote/dist/chunk-AKJME7CQ.js:13379:77)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
[47152] Connected to remote server using StreamableHTTPClientTransport
[47152] Local STDIO server running
[47152] Proxy established successfully between local STDIO and remote StreamableHTTPClientTransport
[47152] Press Ctrl+C to exit
[47152] [Local→Remote] initialize
[47152] {
  "jsonrpc": "2.0",
  "id": 0,
  "method": "initialize",
  "params": {
    "protocolVersion": "2025-06-18",
    "capabilities": {},
    "clientInfo": {
      "name": "claude-ai (via mcp-remote 0.1.29)",
      "version": "0.1.0"
    }
  }
}
[47136] [Remote→Local] 2
2025-09-03T19:09:54.862Z [rebe] [info] Message from server: {"jsonrpc":"2.0","id":2,"error":{"code":0,"message":"method \"prompts/list\" is invalid during session initialization"}} { metadata: undefined }
[47136] [Remote→Local] 3
2025-09-03T19:09:54.865Z [rebe] [info] Message from server: {"jsonrpc":"2.0","id":3,"error":{"code":0,"message":"method \"resources/list\" is invalid during session initialization"}} { metadata: undefined }
[47152] [Remote→Local] 0
2025-09-03T19:09:54.872Z [rebe] [info] Message from server: {"jsonrpc":"2.0","id":0,"result":{"capabilities":{"logging":{},"tools":{"listChanged":true}},"instructions":"1.0","protocolVersion":"2025-06-18","serverInfo":{"name":"my-server","title":"My Server","version":"1.0"}}} { metadata: undefined }
2025-09-03T19:09:54.875Z [rebe] [info] Message from client: {"method":"notifications/initialized","jsonrpc":"2.0"} { metadata: undefined }
2025-09-03T19:09:54.875Z [rebe] [info] Message from client: {"method":"tools/list","params":{},"jsonrpc":"2.0","id":1} { metadata: undefined }
2025-09-03T19:09:54.875Z [rebe] [info] Message from client: {"method":"prompts/list","params":{},"jsonrpc":"2.0","id":2} { metadata: undefined }
2025-09-03T19:09:54.875Z [rebe] [info] Message from client: {"method":"resources/list","params":{},"jsonrpc":"2.0","id":3} { metadata: undefined }
[47152] [Local→Remote] notifications/initialized
[47152] [Local→Remote] tools/list
[47152] [Local→Remote] prompts/list
[47152] [Local→Remote] resources/list
[47152] [Remote→Local] 2
2025-09-03T19:09:54.881Z [rebe] [info] Message from server: {"jsonrpc":"2.0","id":2,"error":{"code":0,"message":"method \"prompts/list\" is invalid during session initialization"}} { metadata: undefined }
[47152] [Remote→Local] 3
2025-09-03T19:09:54.886Z [rebe] [info] Message from server: {"jsonrpc":"2.0","id":3,"result":{"resources":[]}} { metadata: undefined }
[47152] [Remote→Local] 1
2025-09-03T19:09:54.887Z [rebe] [info] Message from server: {"jsonrpc":"2.0","id":1,"result":{"tools":[{"annotations":{},"inputSchema":{"type":"object","required":["n1","n2","n3"],"properties":{"n1":{"type":"string","description":"n1"},"n2":{"type":"string","description":"n2"},"n3":{"type":"string","description":"n3"}},"additionalProperties":false},"name":"create_message","outputSchema":{"type":"object","required":["result"],"properties":{"result":{"type":"string","description":"result of the tool"}},"additionalProperties":false},"title":"create message"},{"annotations":{},"inputSchema":{"type":"object","required":["email"],"properties":{"email":{"type":"string","description":"the email of user"}},"additionalProperties":false},"name":"send_message","title":"Send message"},{"annotations":{},"inputSchema":{"type":"object","required":["email"],"properties":{"email":{"type":"string","description":"the email of user"}},"additionalProperties":false},"name":"send_message2","title":"Send message 2"}]}} { metadata: undefined }
2025-09-03T19:09:59.851Z [rebe] [info] Message from client: {"jsonrpc":"2.0","method":"notifications/cancelled","params":{"requestId":1,"reason":"McpError: MCP error -32001: Request timed out"}} { metadata: undefined }
[47136] [Local→Remote] notifications/cancelled
[47136] [Remote→Local] notifications/tools/list_changed
2025-09-03T19:10:00.738Z [rebe] [info] Message from server: {"jsonrpc":"2.0","method":"notifications/tools/list_changed","params":{}} { metadata: undefined }
[47152] [Remote→Local] notifications/tools/list_changed
2025-09-03T19:10:00.739Z [rebe] [info] Message from server: {"jsonrpc":"2.0","method":"notifications/tools/list_changed","params":{}} { metadata: undefined }

[findleyr]

@rebaz94 this looks like it might be the problem, since it is actually request 1 (the tools/list) that is failing, and may be corrupting the stream:

[47136] Error from remote server: TypeError: Cannot read properties of undefined (reading 'tools')
    at transformResponseFunction (file:///Users/rebo/.npm/_npx/1a3c4333f3a90708/node_modules/mcp-remote/dist/chunk-AKJME7CQ.js:13738:31)
    at Object.interceptResponse (file:///Users/rebo/.npm/_npx/1a3c4333f3a90708/node_modules/mcp-remote/dist/chunk-AKJME7CQ.js:13699:39)
    at transportToServer.onmessage (file:///Users/rebo/.npm/_npx/1a3c4333f3a90708/node_modules/mcp-remote/dist/chunk-AKJME7CQ.js:13765:40)
    at processStream (file:///Users/rebo/.npm/_npx/1a3c4333f3a90708/node_modules/mcp-remote/dist/chunk-AKJME7CQ.js:13379:77)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)

I'd love to see the actual response from the server's perspective, to understand what Claude is failing to unmarshal. When I get back, I'll send detailed instructions for how to grab this (need an hour or so).

[findleyr]

Here's how you can grab logs from the server's perspective: wrap your transport in an mcp.LoggingTransport, like this:

  f, err := os.Create("/tmp/mcp.log")                                                                                                                                                                                                   
  if err != nil {                                                                                                                                                                                                                       
    log.Fatal(err)                                                                                                                                                                                                                      
  }                                                                                                                                                                                                                                     
  defer f.Close()                                                                                                                                                                                                                       
  transport := &mcp.LoggingTransport{Transport: serverTransport, Writer: f}

Then logs of the transport's view of the jsonrpc2 stream will be written to "/tmp/mcp.log". Id be very curious about what the server sees.

[rebaz94]

sorry I'm using NewStreamableHTTPHandler. I don't see any option to enable logging?