MCP in Claude Desktop

Add Onto as a custom connector: paste one URL and sign in with your Onto account. No key to paste, nothing to install.

https://api.buildonto.dev/mcp

The local server (@ontosdk/mcp, Node 20+) runs on your machine and uses an API key instead of a sign-in. Get a key at app.buildonto.dev/read/keys — the server exits straight away without ONTO_API_KEY. In Claude Desktop, open Settings → Developer → Edit Config and add:

{
  "mcpServers": {
    "onto": {
      "command": "npx",
      "args": ["-y", "@ontosdk/mcp@latest"],
      "env": {
        "ONTO_API_KEY": "onto_sk_live_YOUR_KEY"
      }
    }
  }
}

Then fully quit and reopen Claude. On macOS the close button only hides the window — Cmd+Q quits. On Windows, quit from the system tray.

Two different Anthropic products, same vendor. Claude Desktop is the macOS / Windows desktop app (chat UI); Claude Code is the CLI / IDE extension. Both connect to Onto by URL, in different places:

Open a new chat and check the tools menu in the input area. Onto should list all six tools: read_url, read_and_score, score_url, extract_data, map_site, and batch.