Pi for Excel adds AI sidebar to Microsoft spreadsheets

Pi for Excel is a new AI sidebar for spreadsheets

An open-source AI add-in called Pi for Excel is now available. It puts a multi-model AI assistant directly into Microsoft Excel's sidebar.

The tool can read a workbook, make changes, and perform research. Users can connect it to major AI providers by bringing their own API key or using OAuth.

How the AI interacts with your data

The agent operates using 16 built-in tools to interact with spreadsheets. It automatically receives context before each action.

This includes a workbook blueprint, the user's current cell selection, and recent changes. The goal is to eliminate the need for manual descriptions.

A key safety feature is automatic recovery checkpoints. The tool snapshots affected cells before any mutation, allowing a one-click revert from the sidebar if something goes wrong.

Core features and user control

The sidebar supports multiple AI models and allows switching between them mid-conversation. Users can manage multiple session tabs per workbook, with history and a `/resume` command.

It includes several user-convenience and safety features:

• Formatting conventions: Define a house style for currency and decimals once, and the AI follows it.
• Slash commands: For actions like `/model`, `/settings`, `/history`, and `/new` session.
• Extensions: Users can install mini-apps from chat, with generated code running in a sandboxed iframe by default.

Setup and installation process

For most users, installation involves downloading a manifest file and adding it to Excel via the "My Add-ins" menu. After loading the add-in, users connect an AI provider to start chatting.

Developers can clone the GitHub repository for local development. The project requires Node.js ≥ 20 and uses a local HTTPS server, which is required by Office.js.

The production version is a static site hosted on Vercel. User updates are automatic when they close and reopen the Excel taskpane.

Technical architecture and security

Pi for Excel is a single-page Office add-in. Its codebase is organized into modules handling tools, context, authentication, and UI.

Security is a noted focus. The design includes a tool execution policy that classifies actions as read or mutate to manage locking. An extension sandbox isolates untrusted code.

The project is open source under the MIT license and was created by Thomas Mustier. It builds on the Pi agent framework by Mario Zechner.