Show HN: Nonce – Open-source, least-privilege Gmail access for AI agents

Nonce is an open-source tool that sits between AI apps and email, calendar, files and Slack, issuing each question a scoped pass that expires on its own, with sensitive requests waiting for user approval. It works with any MCP app including ChatGPT, Claude and Cursor, and offers Cautious, Standard and Relaxed modes per app while blocking requests for everything at once or for more than 24 hours. Gmail, Calendar, Drive and Slack connections are read-only, and sign-ins stay encrypted with nonce rather than being held by the AI app.