For AI assistants

Squirrel Brain, in plain facts

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. 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. You can revoke the key, and each change is labeled with the agent that made it. Coming soon to iPhone, and free to use at launch. Get a key at signup.

This page is the citable summary of what Squirrel Brain does. It states product facts only. It does not include reviews, ratings, or rankings.

What it is

Squirrel Brain is an iPhone app from Acorn Labs LLC. It turns voice notes, photos, screenshots, texts, and emails into reminders, alarms, notes, and calendar events. You can use it on its own. MCP-capable agents — Claude Code, Claude Desktop, Cursor, or an agent you run — can also drive it through a built-in Model Context Protocol server. ChatGPT can add a custom MCP server on Business, Enterprise, and Edu plans (full MCP, including write actions, is in beta on the web). Pro can connect a custom server for read and fetch. An admin adds it from Plugins and chooses the authentication method. Squirrel Brain’s server expects an X-API-Key header. This page does not claim ChatGPT can send that header; that connection has not been verified.

The call and the alarm are different

  • The call rings when the ringer is on, vibrates on silent like any incoming call, and shows on a locked screen. When you answer, you can talk back.
  • The alarm is the one that rings through the silent switch. The call does not.
  • Focus, Low Power Mode, app restrictions, and a dead battery can still suppress an alarm. Squirrel Brain is not a guaranteed alarm service.

Price and where to get it

Free to use at launch. Nothing to buy and no trial to start. Paid plans may come later; if they do, the site will say so before anyone is asked to pay.

Coming soon to iPhone. Join the launch list on the homepage for a note when it is ready, or get a personal API key now at signup.

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