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Configure Claude Desktop

Claude Desktop reads MCP servers from a per-user JSON config file.

Locate the config file​

OSPath
macOS~/Library/Application Support/Claude/claude_desktop_config.json
Windows%APPDATA%\Claude\claude_desktop_config.json
Linux~/.config/Claude/claude_desktop_config.json

If the file doesn't exist, create it.

Add the server​

{
  "mcpServers": {
    "onesource": {
      "command": "npx",
      "args": ["-y", "@one-source/mcp@latest"],
      "env": { "ONESOURCE_API_KEY": "sk_…" }
    }
  }
}

If mcpServers already exists, add "onesource" as a new key inside it.

Windows note: if npx doesn't launch directly from JSON on your machine, swap the command form:

"command": "cmd",
"args": ["/c", "npx", "-y", "@one-source/mcp@latest"],

Restart Claude Desktop​

Fully quit the app (Cmd-Q / right-click tray → Quit) and reopen. MCP servers are loaded on launch.

What these fields mean:

  • command: the program to run (npx fetches and runs npm packages).
  • args: arguments to that program (-y auto-confirms the install).
  • env: environment variables passed through to the server process.

Verify​

Start a new chat and ask: "Call 1s_setup_check." You should see a tool-use card with Status: Configured (API key).

If you don't see the tool offered:

  • Confirm claude_desktop_config.json is valid JSON (use a linter: a stray comma will silently break all servers, not just onesource).
  • Check Settings → Developer → MCP Logs for boot errors.
  • Fully quit Claude Desktop and reopen; closing the window isn't enough. macOS: Cmd+Q. Windows: right-click the tray icon → Quit.

Troubleshooting​

Server not showing up​

  • Bad JSON. Validate the file at jsonlint.com.
  • Didn't fully restart. Use Cmd+Q (macOS) or Quit-from-tray (Windows).
  • Node.js missing. Run node --version in a terminal. If missing, install from nodejs.org (LTS).

"Command not found" / "npx not found"​

Node.js isn't on the system PATH. Restart your computer after installing Node.js. On Windows, re-run the installer with "Add to PATH" checked.

Tool calls fail​

  • Network. The server has to reach api.onesource.io.
  • Smoke-test directly. In a terminal: ONESOURCE_API_KEY=sk_… npx -y @one-source/mcp@latest. If it boots without errors, the package itself is healthy; the issue is in the Claude config. Ctrl+C to stop.

Next​