Pi for Excel

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Open-source, multi-model AI sidebar add-in for Microsoft Excel. Powered by Pi.

Pi for Excel is an AI agent that lives inside Excel. It reads your workbook, makes changes, and does research — using any model you choose. Bring your own API key or OAuth login for Anthropic, OpenAI, Google Gemini, or GitHub Copilot.

Features

Core spreadsheet tools — 16 built-in tools that the AI can call to interact with your workbook:

Tool	What it does
get_workbook_overview	Structural blueprint — sheets, headers, named ranges, tables, charts, pivots
read_range	Read cells in compact (markdown), CSV, or detailed (with formatting) mode
write_cells	Write values/formulas with overwrite protection and auto-verification
fill_formula	AutoFill a formula across a range (relative refs adjust automatically)
search_workbook	Find text, values, or formula references across all sheets
modify_structure	Insert/delete rows/columns, add/rename/delete/hide sheets
format_cells	Apply formatting — fonts, colors, number formats, borders, named styles
conditional_format	Add or clear conditional formatting rules
trace_dependencies	Trace formula lineage (precedents upstream or dependents downstream)
explain_formula	Plain-language formula explanation with cited cell references
view_settings	Gridlines, headings, freeze panes, tab color, sheet visibility
comments	Read, add, update, reply, resolve/reopen cell comments
workbook_history	List/restore automatic in-between-saves backups for workbook mutations
instructions	Persistent user-level and workbook-level guidance for the AI
conventions	Configurable formatting defaults (currency, negatives, zeros, decimal places)
skills	Bundled Agent Skills for task-specific workflows

Multi-model support — use any supported provider; switch models mid-conversation:

• Anthropic (Claude) — API key or OAuth
• OpenAI / OpenAI Codex — API key
• Google Gemini — API key
• GitHub Copilot — OAuth
• Custom OpenAI-compatible gateways — configure endpoint + model + API key in /settings

Session management — multiple session tabs per workbook, auto-save/restore, session history, /resume to pick up where you left off.

Auto-context injection — the AI automatically receives the workbook blueprint, your current selection, and recent cell changes before every turn. No need to manually describe what you're looking at.

Workbook recovery — automatic checkpoints before every mutation. One-click revert from the sidebar if something goes wrong.

Formatting conventions — define your house style once (currency symbol, negative style, decimal places) and the AI follows it automatically.

Slash commands — /model, /login, /settings, /rules, /extensions, /tools, /export, /compact, /new, /resume, /history, /shortcuts, and more.

Extensions — install sidebar extensions (mini-apps) from chat. The AI can generate and install extension code directly via the extensions_manager tool. Extensions run in an iframe sandbox by default.

Integrations — opt-in external tool integrations:

• Web Search (Jina default, Serper/Tavily/Brave) + fetch_page — find and read external sources without leaving Excel
• MCP Gateway — connect to user-configured MCP servers for custom tool access

Bridge + advanced controls (managed via /experimental):

• Tmux bridge settings — configure bridge URL/token and run health checks
• Python / LibreOffice bridge settings — configure bridge URL/token
• Advanced extension controls — remote URL opt-in, sandbox rollback, and Widget API v2

Files workspace — shared artifact storage across sessions (built-in docs under assistant-docs/ are read-only). Pi's writes and deletes ask for approval in Confirm mode, and in Auto mode whenever they would overwrite or delete a file Pi did not create in this chat.

(Web Search + MCP are managed in /tools, or /extensions → Connections.)

Install

1. Download manifest.prod.xml
2. Add it to Excel — see install guide for step-by-step instructions (macOS + Windows)
3. Click Open Pi in the ribbon
4. Connect a provider (API key or OAuth), or configure a custom OpenAI-compatible gateway in /settings
5. Start chatting — try What sheets do I have? or Summarize my current selection

Developer Quick Start

Prerequisites

• Node.js ≥ 22.19.0 (or ≥24), matching package.json engines
• mkcert — for local HTTPS (required by Office.js)

Setup

git clone https://github.com/tmustier/pi-for-excel.git
cd pi-for-excel
npm install

# Generate local HTTPS certs (Office.js requires HTTPS)
mkcert -install   # one-time CA setup
mkcert localhost   # creates localhost.pem + localhost-key.pem
mv localhost-key.pem key.pem
mv localhost.pem cert.pem

Run

npm run dev        # Vite dev server on https://localhost:3141

Note: the dev port is 3141 (π) — deliberately off the crowded :3000. If you sideloaded a manifest before the move from :3000, re-copy manifest.xml into Excel's wef folder and fully restart Excel.

Optional: prefer a stable named URL (https://pi-excel.localhost, no mkcert, no fixed port)? See docs/portless.md for the opt-in portless flow.

Then sideload the dev manifest into Excel:

macOS (Microsoft docs):

cp manifest.xml ~/Library/Containers/com.microsoft.Excel/Data/Documents/wef/

Then open Excel → Insert → My Add-ins → Pi for Excel.

Windows (Microsoft docs):

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