MCP in Cursor

Two ways to add Onto: the Cursor settings UI, or edit ~/.cursor/mcp.json directly.

Install steps

Get an API key

Grab a key from app.buildonto.dev/read/keys. Free tier: 1,000 requests / month.

Add the server

Via UI: Cursor → Settings → Features → Model Context Protocol → "Add server". Paste:

json

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

Restart Cursor

Fully quit (Cmd+Q / Ctrl+Q) and reopen.

Or edit the file directly

OS	Path
macOS	~/.cursor/mcp.json
Windows	%USERPROFILE%\.cursor\mcp.json
Linux	~/.cursor/mcp.json

Same mcpServers shape as above. Restart Cursor after saving.

Verify

Open Composer or Chat and ask: "What MCP tools are available?" All six — read_url, score_url, read_and_score, batch, map_site, extract_data — should appear.

◈

Try it: "Use Onto to read https://docs.cursor.com and summarize the @-symbol reference."