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

• 148 document tools — read content, edit text, manage styles, insert images, handle tables, charts, conditional formatting, hyperlinks, track changes, navigate headings, search, and more
• 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

Module	Description
core	Document access, config, events, formatting
writer	Content editing, comments, styles, tables, change tracking
writer.nav	Heading tree, bookmarks, proximity navigation
writer.index	Full-text search with Snowball stemming
calc	Cells, sheets, formulas, charts, conditional formatting, comments
draw	Shapes, pages, slides, placeholders, master slides, transitions (Draw and Impress)
images	Image generation and editing (pluggable providers)
batch	Multi-tool execution with variable chaining
http	Shared HTTP server with optional SSL
mcp	MCP JSON-RPC protocol handler
tunnel	Tunnel manager (ngrok, Cloudflare, bore, Tailscale)

Development

./install.sh              # Set up dev environment
make deploy               # Build + install + restart LO + show log
make test                 # Run tests

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

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 License.txt.