Connection to MongoDB MCP Server always show error despite being successful

[olishiz]

Describe the bug
The bug is about making a connection and listening between MongoDB MCP Server and MCP Inspector. I have my Windsurf serving my mongodb mcp server using the following mcpServers:

    "MongoDB": {
      "command": "npx",
      "args": [
        "-y",
        "mongodb-mcp-server",
        "--connectionString",
        "mongodb://localhost:27017/",
        "--readOnly"
      ]
    },

To Reproduce
Steps to reproduce the behavior:

1. Use Windsurf and append ur mcpServers here as follow:

{
  "mcpServers": {
    "MongoDB": {
      "command": "npx",
      "args": [
        "-y",
        "mongodb-mcp-server",
        "--connectionString",
        "mongodb://localhost:27017/",
        "--readOnly"
      ]
    },
    "time": {
      "command": "uvx",
      "args": [
        "mcp-server-time"
      ],
      "env": {}
    },
    "context7": {
      "command": "npx",
      "args": ["-y", "@upstash/context7-mcp"]
    },
    "browsermcp": {
      "command": "npx",
      "args": ["@browsermcp/mcp@latest"]
    }
  }
}

Expected behavior
I want to go into the portal - without having this DEBUG issue or not allowing me to inspect my mongodb collections - i want to test out the tools

Logs
If applicable, add logs to help explain your problem.

Opening browser...
New STDIO connection request
Query parameters: {"command":"npx","args":"-y mongodb-mcp-server@latest --connectionString mongodb://localhost:27017 --readOnly","env":"{\"HOME\":\"/Users/00140216oliversimchoohowe\",\"LOGNAME\":\"00140216oliversimchoohowe\",\"PATH\":\"/Users/00140216oliversimchoohowe/Development/inspector/node_modules/.bin:/Users/00140216oliversimchoohowe/Development/inspector/server/node_modules/.bin:/Users/00140216oliversimchoohowe/Development/inspector/node_modules/.bin:/Users/00140216oliversimchoohowe/Development/node_modules/.bin:/Users/00140216oliversimchoohowe/node_modules/.bin:/Users/node_modules/.bin:/node_modules/.bin:/opt/homebrew/lib/node_modules/npm/node_modules/@npmcli/run-script/lib/node-gyp-bin:/Users/00140216oliversimchoohowe/Development/inspector/node_modules/.bin:/Users/00140216oliversimchoohowe/Development/node_modules/.bin:/Users/00140216oliversimchoohowe/node_modules/.bin:/Users/node_modules/.bin:/node_modules/.bin:/opt/homebrew/lib/node_modules/npm/node_modules/@npmcli/run-script/lib/node-gyp-bin:/opt/homebrew/opt/postgresql@14/bin:/Users/00140216oliversimchoohowe/.codeium/windsurf/bin:/opt/homebrew/bin:/opt/homebrew/sbin:/Users/00140216oliversimchoohowe/.nvm/versions/node/v22.15.0/bin:/usr/local/bin:/System/Cryptexes/App/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/local/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/appleinternal/bin:/Library/Apple/usr/bin:/usr/local/sbin:/opt/homebrew/opt/postgresql@14/bin:/Users/00140216oliversimchoohowe/.codeium/windsurf/bin:/Users/00140216oliversimchoohowe/Library/Application Support/JetBrains/Toolbox/scripts\",\"SHELL\":\"/bin/zsh\",\"TERM\":\"xterm-256color\",\"USER\":\"00140216oliversimchoohowe\"}","transportType":"stdio"}
STDIO transport: command=/opt/homebrew/bin/npx, args=-y,mongodb-mcp-server@latest,--connectionString,mongodb://localhost:27017,--readOnly
Created server transport
Created client transport
Received POST message for sessionId de65190b-7463-4bfb-9c91-3d6df390c54c
Received POST message for sessionId de65190b-7463-4bfb-9c91-3d6df390c54c
Received POST message for sessionId de65190b-7463-4bfb-9c91-3d6df390c54c

As you can see, the MongoDB MCP Server is connected and able to listen to the MCP client

Additional context

As seen here:

[ronantakizawa]

@olishiz
After investigating this issue, I found that the problem is in the MongoDB MCP Server, not the MCP Inspector.

The MongoDB MCP Server incorrectly declares logging capability without implementing the required methods:

File: mongodb-mcp-server/src/server.ts:51

  // ❌ INCORRECT - declares logging capability but doesn't implement it
  this.mcpServer.server.registerCapabilities({
    logging: {},
    resources: { listChanged: true, subscribe: true }
  });

The MongoDB MCP Server:

• ✅ Declares "logging": {} capability
• ❌ Does NOT implement logging/setLevel method
• ❌ Does NOT emit any notifications/message log notifications

What Happens

1. MongoDB MCP Server declares logging capability during initialization
2. MCP Inspector sees the capability and tries to call logging/setLevel
3. Server returns MethodNotFound error since it's not implemented
4. Inspector shows connection as failed despite successful connection

I implemented a fix in the MongoDB MCP Server here: mongodb-js/mongodb-mcp-server#455