Nelson MCP

A LibreOffice extension that turns your documents into an MCP server. External AI clients connect over HTTP and get full access to document tools — reading, editing, navigating, formatting, and more.

Works with any MCP-compatible client: Claude Code, OpenCode, Goose, ollmcp, etc.

How it works

Nelson MCP runs an HTTP server inside LibreOffice and speaks the Model Context Protocol. AI agents connect to it and use tools to interact with your open document — no copy-paste, no file export.

┌─────────────────┐     HTTP/MCP     ┌────────────────┐
│  AI Client      │ ───────────────► │  LibreOffice   │
│  (Claude Code,  │    tools/call    │  + Nelson MCP  │
│  OpenCode…)     │ ◄─────────────── │                │
└─────────────────┘   tool results   └────────────────┘

Features

• 140 document tools — read content, edit text, manage styles, insert images, handle tables, charts, conditional formatting, hyperlinks, track changes, page headers/footers, navigate headings, search, and more. The list is filtered by the active document type, so a client sees only what applies (94 with a Writer document, 48 with Calc)
• Custom MCP endpoints — expose only the tools your agent needs. Built-in presets (minimal, writer-edit, writer-read, calc, gallery) or create your own filtered endpoints
• Writer, Calc, Draw, Impress — tools adapt to the active document type
• Calc =PROMPT() — call an LLM directly from a spreadsheet cell
• Built-in launchers — launch Claude Code, Gemini CLI, or OpenCode directly from LibreOffice with one click. Nelson handles MCP config, prompt injection, and working directory setup automatically
• AI image generation — generate and edit images from text prompts using Stable Diffusion (A1111/Forge), OpenAI, or AI Horde. One-click detect/install/launch for Automatic1111
• Beginner-friendly setup — all tools come with install buttons, auto-detection of existing installations, and guided configuration. No manual config files to edit
• Tunnels — expose the MCP server externally via ngrok, Cloudflare, bore, or Tailscale
• SSL — optional HTTPS with auto-generated certificates
• Modular — each feature is a self-contained module with its own config, services, and tools

Install

1. Download the latest .oxt from the releases page
2. In LibreOffice: Tools > Extension Manager > Add
3. Restart LibreOffice
4. The MCP server starts automatically (default: http://localhost:8766/mcp)

Quick start

Once installed, point your MCP client at the server:

{
  "mcpServers": {
    "nelson": {
      "type": "http",
      "url": "http://localhost:8766/mcp"
    }
  }
}

Open a document in LibreOffice, then ask your AI client to read or edit it.

For AI agents: see QUICKSTART.md — a step-by-step guide for LLM agents on how to discover documents, navigate structure, and use tools effectively.

Modules

Around 30 modules; the main ones:

Turning off what you do not use

Nelson ships a lot of tools, but a client never sees all of them, and most of
the narrowing happens on its own. In order of how much they cut:

So a Calc user is already down to 48 tools without touching anything, and a
custom endpoint takes that to whatever you like.

What Nelson deliberately does not have is a switch to stop a module
loading. It would be a seventh overlapping control, and it would buy very
little: a full startup is ~370 ms for 31 modules, and the optional families
are already invisible in the tool list. See
#29 for the measurements.

Development

./install.sh              # Set up dev environment
make deploy               # Build + install + restart LO + show log
make test                 # Run tests
make release              # Tag, build and publish a release (see scripts/release.sh)

See DEVEL.md for the complete developer guide and docs/modules.md for the module framework reference.

Developing with an AI agent

This project is developed with AI coding agents, using
wbox-mcp to make that practical.

Nelson lives inside LibreOffice, so an agent cannot verify a change without
actually running LibreOffice — and a headless process cannot show whether a
logo really landed in the page header. wbox-mcp is an MCP server that hands the
agent a sandboxed LibreOffice in a nested Wayland compositor: it can kill,
deploy and relaunch the extension, drive the UI, read the Nelson log, and take
screenshots of the result.

That closes the loop. The agent edits the code, redeploys, calls the tool
through MCP, and looks at the rendered document to confirm the change —
instead of assuming it worked.

Documentation

• QUICKSTART.md — agent guide: discovery, workflows, tool patterns
• AGENTS.md — developer cheatsheet: project structure, build pipeline, critical rules
• docs/howto/ — user guides: Tailscale + ChatGPT, Forge, Ollama indexation, image galleries
• docs/roadmap.md — what's planned next
• CHANGELOG.md — version history

Acknowledgments

Nelson MCP is the result of merging and reworking two other projects:

• LocalWriter — a LibreOffice extension that embedded a chatbot sidebar with AI providers (OpenAI-compatible APIs, Ollama, AI Horde). Originally created as LibreCalc AI Assistant by Umut Çelik, then forked and expanded by @balisujohn and significantly developed by @KeithCu (Keith Curtis) who added AI Horde support, multi-provider management, the chatbot sidebar, and Calc =PROMPT() integration. The module framework, the tool system, and the per-module config architecture were developed by @quazardous.

• mcp-libre — a standalone LibreOffice MCP server that exposed Writer tools to external AI clients via MCP. It demonstrated that the MCP approach (external AI + document tools) was more flexible than an embedded chatbot. Nelson MCP adopts this MCP-first architecture: the chatbot and AI provider modules have been removed, and the extension focuses entirely on being a tool server for external clients.

License

MPL 2.0 — see extension/registration/license.txt.