mcp-clickhouse - ERROR - Failed to connect to ClickHouse: HTTP driver received HTTP status 400, server response: Port 9000 is for clickhouse-client program

[khanakia]

I am following this tutorial https://clickhouse.com/docs/use-cases/AI/MCP/claude-desktop to connect the MCP with Claude desktop and getting the error.

Also attaching the MCP log file

{
  "mcpServers": {
    "mcp-clickhouse": {
      "command": "/Library/Frameworks/Python.framework/Versions/3.13/bin/uv",
      "args": [
        "run",
        "--with",
        "mcp-clickhouse",
        "--python",
        "3.10",
        "mcp-clickhouse"
      ],
      "env": {
        "CLICKHOUSE_HOST": "xxx.us-east-1.aws.clickhouse.cloud",
        "CLICKHOUSE_PORT": "8443",
        "CLICKHOUSE_USER": "default",
        "CLICKHOUSE_PASSWORD": "password",
        "CLICKHOUSE_SECURE": "true",
        "CLICKHOUSE_VERIFY": "true",
        "CLICKHOUSE_CONNECT_TIMEOUT": "30",
        "CLICKHOUSE_SEND_RECEIVE_TIMEOUT": "30"
      }
    }
  }
}

mcp-server-mcp-clickhouse.log

[ezotrank]

You need to change your port. The 8443 is for the native ClickHouse client. You might try 8444 or check which one is exposed.

[khanakia]

This is what Clickhouse Cloud Console gives me when i click Connect button so the Port is correct

curl --user 'default:<password>' \
  --data-binary 'SELECT 1' \
  https://xxx.us-east-1.aws.clickhouse.cloud:8443

[sankalpsthakur]

I've opened a PR that improves connection failure diagnostics for cases like the native-protocol / HTTP port confusion here (and related CLICKHOUSE_SECURE mix-ups):

#212

When the client fails to connect, the error now includes short Hint: lines pointing at HTTP ports (8123/8443) vs native TCP (9000/9440), and clarifying that CLICKHOUSE_SECURE is for the database connection only.

Note: for ClickHouse Cloud, 8443 is the correct HTTPS HTTP-interface port (as in your curl example). If you still see Port 9000 is for clickhouse-client with Cloud settings, that usually means traffic is not reaching the HTTP interface you intended — the new hints should make that clearer in the server logs.