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Ecosystem

One format, many surfaces.

The Python package does the reading and writing; the other tools wrap it. A second writer in JavaScript, written from the spec alone, passes the same conformance kit.

CLI

Encode, decode, validate and compare sizes, in batch or in CI.

cellprose encode book.xlsx
cellprose decode book.sheet.md
cellprose check book.sheet.md
cellprose stats book.xlsx

Python

The core library, for pipelines.

import cellprose
text = cellprose.dumps("book.xlsx")

MCP server

Agents list sheets, read workbooks as Cellprose, and write cells back to .xlsx.

pip install -e ".[mcp]"
claude mcp add cellprose -- cellprose-mcp

For agents: llms.txt

An index of the format for agents, and the spec, skill and install steps in one file.

/llms.txt
/llms-full.txt

Agent skill

A short SKILL.md that teaches an agent the blocks, so it needs no spec lookup.

skills/cellprose/SKILL.md

Git

Readable diffs for .xlsx files already in a repo, and a pre-commit hook that writes a .sheet.md twin.

cellprose git-setup
cellprose pre-commit

JavaScript writer

An independent writer with no dependencies. It runs this site's playground.

node js/bin/cellprose-encode.js book.xlsx

GitHub viewer

A browser extension for .sheet.md files on GitHub: sheet tabs, and click a cell to see its real formula and the cells it reads.

viewer/extension

Conformance kit

Language-neutral cases (JSON workbooks, expected .sheet.md, decoded cells) and a checker, for writers and readers in other languages.

python conformance/check.py --encoder "your-encoder"

Cellprose is an open format for spreadsheet workbooks. Benchmarks: Claude Haiku 5.5 and Sonnet 5.5, 14 workbooks, two same-session repeats.

CellproseGitHub ↗
A1fx
ReadyClick a cell · drag the corner handle · arrow keys move · Esc clears