MCP config builder
Build an MCP servers JSON config for a client without hand-editing.
Runs in this tab. The file stays here.
Paste into your client's MCP settings (for example .cursor/mcp.json or claude_desktop_config.json). Don't commit real API keys.
This runs in your browser. Nothing is uploaded.
About MCP config builder
Build an MCP servers JSON config without hand-editing it: add each server by name, then its command, arguments and environment, or an HTTP URL.
MCP clients read a JSON file that lists the servers they should start or connect to, and a missing comma or a stray quote is a common reason a server doesn't show up. Here you add a server by name, choose between a Command (run a program, with arguments one per line and environment as KEY=value lines) or an HTTP URL, and the page writes the JSON under an mcpServers key. Add as many servers as you need. A filesystem example is filled in to start.
A server with no name is left out, and so is a command server with no command or an HTTP server with no URL, so an unfinished row doesn't produce broken output. Environment lines without an equals sign are skipped. Download saves the result as mcp.json, or you can copy it and paste it into your client's own file.
Where that file lives depends on the client, and some clients use slightly different keys or extra fields, so check yours. Environment values are often API keys; keep them in a file that's private, and don't commit it. The page only writes a config. It doesn't start the server, check that npx can find the package, or tell you whether the client will connect, and for that you have to restart the client and look.
How to use MCP config builder
- 1Add a server, give it a name, and choose Command or HTTP URL.
- 2For a command, enter the program, its arguments one per line, and any environment variables.
- 3Add more servers if you need them.
- 4Copy or download the JSON and place it in your client's MCP config.
What it won't do
- Writes an mcpServers object only; no client-specific extra fields.
- Doesn't run or validate the server.
- Keep secrets out of any file you commit.
Common questions
Does it start or test the server?
No. It only writes the config. Start your client to see whether the server connects, and read the client's log if it doesn't.
Why is my server missing from the JSON?
Servers need a name, and then a command (for the Command type) or a URL (for HTTP). Rows that are missing those are skipped. Environment lines also need an equals sign.
Where do I put the file?
It depends on the client. Cursor reads .cursor/mcp.json in a project, and Claude Desktop uses claude_desktop_config.json. Check the client's documentation if you're not sure, because locations and keys vary.
Related tools
Why this one doesn't upload your file
There is no server to upload to. This page is a static file, and the work happens in your browser using the same graphics and WebAssembly code that renders every other site you visit. Your file is read from disk into memory, processed, and handed back as a download. Once the page has loaded you can disconnect from the network entirely and it keeps working. The longer explanation