Coming soon to iPhone

The calendar your AI agent can use on its own

Squirrel Brain is an agent-friendly calendar and reminder app for iPhone: any MCP client can read and update it on its own with a personal API key. Coming soon to iPhone, and free to use at launch.

Squirrel Brain calendar screen listing upcoming events

What an agent can do

Read the day, then change the calendar

An agent with your key can read today’s agenda, including what is overdue and what is due today. It can list, search, and find notes, tasks, and calendar events. It can add a calendar event with an iPhone alarm, move or reschedule it, change it, mark it done, or cancel it, and it can list the alarms already set. It can save a note, a checklist, or a link, add or remove a line on your forever note, and file a photo onto a board. It can send a banner to your phone and chat with you in the Agent Portal. A change can become a real alarm, a reminder, or a phone call on your iPhone.

How to connect

Three steps, then the agent works

  1. Get a personal key at signup. It is ready right away. You can also make one in the iOS app. Coming soon to iPhone.
  2. Add Squirrel Brain to any MCP client that can send a custom header. Claude Code, Claude Desktop, and Cursor are examples. Setup details are on the MCP page and the developer docs.
  3. The agent reads and updates your calendar on its own.

ChatGPT on Business, Enterprise, and Edu plans can add a custom MCP server. This page does not claim ChatGPT can send the X-API-Key header.

Your key

You can revoke it, and every change is labeled

The key is yours. Revoke it and the agent loses access. Each change is labeled with the agent that made it, so you can see who added or moved an event.

On your iPhone

Saved now, on the phone after it syncs

Server changes are saved right away and reach the phone (and its Calendar) after the app syncs.

Questions

Can an agent update my calendar without me typing it in?

Yes. With a personal API key, an MCP client can add, move, and cancel calendar events on its own. You can revoke the key, and each change is labeled with the agent that made it.

What shows up on my iPhone?

Server changes are saved right away and reach the phone (and its Calendar) after the app syncs. A change can become an alarm, a reminder, or a phone call.

How does an agent connect?

Get a personal key at signup, add Squirrel Brain to any MCP client that can send a custom header, and the agent can read and update the calendar. Claude Code, Claude Desktop, and Cursor are examples.

Can ChatGPT connect?

ChatGPT on Business, Enterprise, and Edu plans can add a custom MCP server. This page does not claim ChatGPT can send the X-API-Key header. That connection has not been verified.

Is the iPhone app out, and what does it cost?

Coming soon to iPhone. It is free to use at launch. Nothing to buy and no trial to start. You can get a key now at signup.