Excal AI

Excal AI lets you edit a spreadsheet by talking to it. An AI agent reads, writes, formats and validates cells in a live workbook in your browser, searches the web when it needs facts, and imports and exports Excel files. I built it alone, from the spreadsheet integration to billing.

The problem

The idea was Cursor for spreadsheets. You describe the change, and an agent makes it in the workbook itself. Most assistants instead answer in text that you then have to apply by hand, cell by cell.

What it does

• A live workbook in the browser, built on the Univer spreadsheet engine, with XLSX import and export.
• An AI agent with tool calling. It edits values and ranges, formatting, data validation and sheets, and streams its work as it goes.
• Web search and calculation when a request needs facts or exact maths.
• Accounts and subscriptions, with saved conversation history.

How it works

When the model calls a tool that changes the sheet, the call runs in the browser against the live workbook, and the result is fed back into the conversation. Tools that need the network, like search, run on the server.

Key decisions

• Run edits where the data lives. Because workbook tools execute in the browser, the agent edits exactly what the user sees, and there's no server copy of the sheet to keep in sync.
• Send the model only what matters. The sheet is serialized compactly, non-empty cells only, so large workbooks fit in the model's context.
• Typed tools. Every tool has a schema that validates the model's arguments before anything touches the workbook.

Excal AI is live at excal-ai.vercel.app (opens in a new tab).