Question 1

What is claude_desktop_config.json and where does it live?

Accepted Answer

claude_desktop_config.json is the MCP server registry file that Claude Desktop reads on startup. On macOS it lives at ~/Library/Application Support/Claude/claude_desktop_config.json. On Windows it is at %APPDATA%\Claude\claude_desktop_config.json. The file lists every MCP server Claude should connect to, along with the transport type, command path, arguments, and environment variables for each.

Question 2

What is the difference between stdio and SSE transport in MCP?

Accepted Answer

stdio (standard I/O) runs the MCP server as a local subprocess. Claude Desktop spawns the process, communicates via stdin/stdout, and the server exits when Claude closes. SSE (Server-Sent Events) connects to a remote MCP server over HTTP. Use stdio for local tools and scripts; use SSE for hosted or shared MCP servers accessible over the network.

Question 3

How do I add multiple MCP servers to claude_desktop_config.json?

Accepted Answer

The config file holds a mcpServers object where each key is a unique server name you choose. Add as many entries as you need: {"mcpServers":{"filesystem":{...},"github":{...},"custom-tool":{...}}}. Each entry is independent — Claude Desktop initializes all listed servers at startup. Use this generator to build each block, then merge them into the mcpServers object manually.

Question 4

Why does Claude Desktop say it cannot find my MCP server after I saved the config?

Accepted Answer

The three most common causes are: (1) the command path is wrong — use the absolute path to the executable, not a shell alias; (2) Claude Desktop was not fully restarted after saving the config — quit and reopen it; (3) the config JSON has a syntax error (trailing comma, mismatched brace) — paste it into a JSON validator to confirm it is valid before debugging further.

Question 5

Can I use environment variables for API keys in the MCP server config?

Accepted Answer

Yes. Each server entry accepts an env object where you can pass environment variables to the subprocess. Example: {"command":"npx","args":["-y","@my-org/mcp-server"],"env":{"API_KEY":"your-key-here"}}. This is the recommended approach — do not hardcode secrets in the args array where they may appear in process lists.

Question 6

Does the MCP Config Generator send my server details anywhere?

Accepted Answer

No. The generator runs entirely in your browser with zero network calls. Your server name, command path, arguments, and environment variable values never leave your tab. The generated JSON is produced in JavaScript locally and copied directly to your clipboard.

Build your MCP server config, paste and go.

Fill in the form. Copy the JSON.

20-40 minutes of config debugging, gone.