# MCP-NixOS - Because Your AI Shouldn't Hallucinate Package Names

[![MCP Toplist](https://mcptoplist.com/badge/glama%2Futensils%2Fmcp-nixos.svg)](https://mcptoplist.com/server/glama%2Futensils%2Fmcp-nixos)

[![CI](https://github.com/utensils/mcp-nixos/actions/workflows/ci.yml/badge.svg)](https://github.com/utensils/mcp-nixos/actions/workflows/ci.yml)
[![codecov](https://codecov.io/gh/utensils/mcp-nixos/graph/badge.svg?token=kdcbgvq4Bh)](https://codecov.io/gh/utensils/mcp-nixos)
[![PyPI](https://img.shields.io/pypi/v/mcp-nixos.svg)](https://pypi.org/project/mcp-nixos/)
[![FlakeHub](https://img.shields.io/endpoint?url=https://flakehub.com/f/utensils/mcp-nixos/badge)](https://flakehub.com/flake/utensils/mcp-nixos)
[![Python 3.11+](https://img.shields.io/badge/python-3.11+-blue.svg)](https://www.python.org/downloads/)
![CodeRabbit Pull Request Reviews](https://img.shields.io/coderabbit/prs/github/utensils/mcp-nixos?utm_source=oss&utm_medium=github&utm_campaign=utensils%2Fmcp-nixos&labelColor=171717&color=FF570A&link=https%3A%2F%2Fcoderabbit.ai&label=CodeRabbit+Reviews)
[![Built with Claude](https://img.shields.io/badge/Built%20with-Claude-D97757?logo=claude&logoColor=white)](https://claude.ai)

## Quick Start

**🚨 No Nix/NixOS Required!** Works on any system - Windows, macOS, Linux. You're just querying APIs.

### Option 1: uvx (Recommended)

[![Install MCP Server](https://cursor.com/deeplink/mcp-install-dark.svg)](https://cursor.com/install-mcp?name=nixos&config=eyJjb21tYW5kIjoidXZ4IG1jcC1uaXhvcyJ9)

```json
{
  "mcpServers": {
    "nixos": {
      "command": "uvx",
      "args": ["mcp-nixos"]
    }
  }
}
```

### Option 2: Nix

[![Install MCP Server](https://cursor.com/deeplink/mcp-install-dark.svg)](https://cursor.com/install-mcp?name=nixos&config=eyJjb21tYW5kIjoibml4IHJ1biBnaXRodWI6dXRlbnNpbHMvbWNwLW5peG9zIC0tIn0%3D)

```json
{
  "mcpServers": {
    "nixos": {
      "command": "nix",
      "args": ["run", "github:utensils/mcp-nixos", "--"]
    }
  }
}
```

### Option 3: Docker

[![Install MCP Server](https://cursor.com/deeplink/mcp-install-dark.svg)](https://cursor.com/install-mcp?name=nixos&config=eyJjb21tYW5kIjoiZG9ja2VyIiwiYXJncyI6WyJydW4iLCItLXJtIiwiLWkiLCJnaGNyLmlvL3V0ZW5zaWxzL21jcC1uaXhvcyJdfQ%3D%3D)

```json
{
  "mcpServers": {
    "nixos": {
      "command": "docker",
      "args": ["run", "--rm", "-i", "ghcr.io/utensils/mcp-nixos"]
    }
  }
}
```

Your AI now has access to real NixOS data instead of making things up. You're welcome.

### Option 4: HTTP (Remote MCP)

FastMCP supports running this server over HTTP at a URL (the MCP endpoint defaults to `/mcp`).

```bash
# Run an HTTP MCP server at http://127.0.0.1:8000/mcp
MCP_NIXOS_TRANSPORT=http MCP_NIXOS_HOST=127.0.0.1 MCP_NIXOS_PORT=8000 mcp-nixos
```

STDIO (default):

```bash
MCP_NIXOS_TRANSPORT=stdio mcp-nixos
```

Custom path:

```bash
MCP_NIXOS_TRANSPORT=http MCP_NIXOS_PATH=/api/mcp mcp-nixos
```

Stateless HTTP (disables per-client session state):

```bash
MCP_NIXOS_TRANSPORT=http MCP_NIXOS_STATELESS_HTTP=1 mcp-nixos
```

### Option 5: Pi Coding Agent

[Pi](https://www.npmjs.com/package/@mariozechner/pi-coding-agent) does not speak MCP natively. Two supported paths:

**A. pi-mcp-adapter (recommended — speaks MCP, single source of truth):**

```bash
pi install npm:pi-mcp-adapter
```

Then add to `~/.pi/agent/mcp.json`:

```json
{
  "mcpServers": {
    "nixos": {
      "command": "uvx",
      "args": ["mcp-nixos"],
      "lifecycle": "lazy"
    }
  }
}
```

**B. Project-local extension (clone + run):** this repo ships `.pi/extensions/mcp-nixos.ts`, auto-loaded when you run `pi` in the cloned repo. Optional: `cd .pi && npm install` for editor type resolution. Pi runs it either way.

## What Is This?

An MCP server providing accurate, real-time information about:

- **NixOS packages** - 130K+ packages that actually exist
- **NixOS options** - 23K+ ways to configure your system
- **Home Manager** - 5K+ options for dotfile enthusiasts
- **nix-darwin** - 1K+ macOS settings Apple doesn't document
- **Nixvim** - 5K+ options for Neovim configuration via [NuschtOS search](https://github.com/NuschtOS/search)
- **NVF** - 2.4K+ Neovim options from its [published unstable documentation](https://nvf.notashelf.dev/options.html)
- **FlakeHub** - 600+ flakes from [FlakeHub.com](https://flakehub.com) registry
- **Noogle** - 2K+ Nix functions with type signatures via [noogle.dev](https://noogle.dev)
- **NixOS Wiki** - Community documentation and guides from [wiki.nixos.org](https://wiki.nixos.org)
- **nix.dev** - Official Nix tutorials and guides from [nix.dev](https://nix.dev)
- **Package versions** - Historical versions with commit hashes via [NixHub.io](https://www.nixhub.io)
- **Binary cache status** - Check if packages are cached on cache.nixos.org with download sizes
- **Local flake inputs** - Explore your pinned flake dependencies directly from the Nix store (requires Nix)

## The Tools

Just two. We consolidated 17 tools into 2 because your AI's context window isn't infinite.

**~1,030 tokens total.** That's it. While other MCP servers are hogging your context like it's Black Friday, we're sipping minimalist tea in the corner. Your AI gets NixOS superpowers without the bloat.

### `nix` - Unified Query Tool

One tool to rule them all:

```text
nix(action, query, source, type, channel, limit, version, system)
```

`version` and `system` are only used by `action="cache"`.

| Action | What it does |
|--------|-------------|
| `search` | Search packages, options, programs, or flakes |
| `info` | Get detailed info about a package or option |
| `stats` | Get counts and categories |
| `browse` | Browse Home Manager, Darwin, Nixvim, NVF, or Noogle by prefix (legacy alias: `options`) |
| `channels` | List available NixOS channels |
| `flake-inputs` | Explore local flake inputs from Nix store |
| `cache` | Check binary cache status for packages |
| `store` | Read files or list directories at an explicit `/nix/store` path (requires Nix) |

| Source | What it queries |
|--------|----------------|
| `nixos` | Packages, options, programs |
| `home-manager` | Home Manager options |
| `darwin` | nix-darwin options |
| `flakes` | Community flakes (search.nixos.org) |
| `flakehub` | FlakeHub registry (flakehub.com) |
| `nixvim` | Nixvim Neovim configuration options |
| `nvf` | NVF Neovim configuration options (latest unstable docs) |
| `noogle` | Nix function signatures and docs (noogle.dev) |
| `wiki` | NixOS Wiki articles (wiki.nixos.org) |
| `nix-dev` | Official Nix documentation (nix.dev) |
| `nixhub` | Package metadata and store paths (nixhub.io) |

NVF results use canonical `vim.*` option paths. Queries may also use the shorthand
`programs.nvf.vim.*` or the NixOS/Home Manager module path
`programs.nvf.settings.vim.*`; both are normalized automatically.

**Examples:**

```python
# Search NixOS packages
nix(action="search", query="firefox", source="nixos", type="packages")

# Get package info
nix(action="info", query="firefox", source="nixos", type="package")

# Search Home Manager options
nix(action="search", query="git", source="home-manager")

# Browse darwin options
nix(action="browse", source="darwin", query="system.defaults")

# Search Nixvim options
nix(action="search", query="telescope", source="nixvim")

# Get Nixvim option info
nix(action="info", query="plugins.telescope.enable", source="nixvim")

# Search NVF options
nix(action="search", query="vim.languages.nix", source="nvf")

# Get NVF option info using a module wrapper path
nix(action="info", query="programs.nvf.settings.vim.languages.nix.enable", source="nvf")

# Browse NVF options below a prefix
nix(action="browse", query="programs.nvf.vim.languages.nix", source="nvf")

# Search FlakeHub
nix(action="search", query="nixpkgs", source="flakehub")

# Get FlakeHub flake info
nix(action="info", query="NixOS/nixpkgs", source="flakehub")

# Search Noogle for Nix functions
nix(action="search", query="mapAttrs", source="noogle")

# Get Noogle function info
nix(action="info", query="lib.attrsets.mapAttrs", source="noogle")

# Browse Noogle function categories
nix(action="browse", source="noogle", query="lib.strings")

# Search NixOS Wiki
nix(action="search", query="nvidia", source="wiki")

# Get Wiki page info
nix(action="info", query="Flakes", source="wiki")

# Search nix.dev documentation
nix(action="search", query="packaging tutorial", source="nix-dev")

# Search NixHub for package metadata
nix(action="search", query="nodejs", source="nixhub")

# Get detailed package info from NixHub (license, homepage, store paths)
nix(action="info", query="python", source="nixhub")

# Check binary cache status
nix(action="cache", query="hello")

# Check cache for specific version
nix(action="cache", query="python", version="3.12.0")

# Check cache for specific system
nix(action="cache", query="firefox", system="x86_64-linux")

# Get stats
nix(action="stats", source="nixos", channel="stable")

# List local flake inputs (requires Nix)
nix(action="flake-inputs", type="list")

# Browse files in a flake input
nix(action="flake-inputs", type="ls", query="nixpkgs:pkgs/by-name")

# Read a file from a flake input
nix(action="flake-inputs", type="read", query="nixpkgs:flake.nix")

# List or read a store path directly (requires Nix)
nix(action="store", type="ls", query="/nix/store/<hash>-<name>")
nix(action="store", type="read", query="/nix/store/<hash>-<name>/flake.nix")
```

### `nix_versions` - Package Version History

Find historical versions with nixpkgs commit hashes. Output includes:
- Package metadata (license, homepage, programs) when available
- Platform availability per version (Linux/macOS)
- Nixpkgs commit hash for reproducible builds
- Attribute path for Nix expressions

```python
nix_versions(package, version, limit)
```

**Examples:**

```python
# List recent versions with metadata
nix_versions(package="python", limit=5)

# Find specific version
nix_versions(package="nodejs", version="20.0.0")
```

## Installation

**You DON'T need Nix installed.** This runs anywhere Python runs.

```bash
# Run directly (no install)
uvx mcp-nixos

# Or install
pip install mcp-nixos
```

For Nix users:

```bash
nix run github:utensils/mcp-nixos
nix profile install github:utensils/mcp-nixos
```

### Declarative Installation (NixOS / Home Manager / nix-darwin)

mcp-nixos is available in [nixpkgs](https://search.nixos.org/packages?channel=unstable&show=mcp-nixos&query=mcp-nixos):

```nix
# NixOS (configuration.nix)
environment.systemPackages = [ pkgs.mcp-nixos ];

# Home Manager (home.nix)
home.packages = [ pkgs.mcp-nixos ];

# nix-darwin (darwin-configuration.nix)
environment.systemPackages = [ pkgs.mcp-nixos ];
```

Or use the flake directly with the provided overlay:

```nix
# flake.nix
{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    mcp-nixos.url = "github:utensils/mcp-nixos";
  };

  outputs = { self, nixpkgs, mcp-nixos, ... }: {
    # Example: NixOS configuration
    nixosConfigurations.myhost = nixpkgs.lib.nixosSystem {
      system = "x86_64-linux";
      modules = [{
        nixpkgs.overlays = [ mcp-nixos.overlays.default ];
        environment.systemPackages = [ pkgs.mcp-nixos ];
      }];
    };

    # Example: Home Manager standalone
    homeConfigurations.myuser = home-manager.lib.homeManagerConfiguration {
      pkgs = import nixpkgs {
        system = "x86_64-linux";
        overlays = [ mcp-nixos.overlays.default ];
      };
      modules = [{
        home.packages = [ pkgs.mcp-nixos ];
      }];
    };
  };
}
```

`overlays.default` only adds `pkgs.mcp-nixos`. The package carries its own
FastMCP 4 / MCP SDK 2 stack (see `nix/fastmcp4.nix`), including a starlette at
or above the 1.0.1 security floor FastMCP requires, so nothing else in your
Python package set changes, even on nixpkgs channels that still ship FastMCP 3.
If you also want `pkgs.python3Packages.fastmcp` itself upgraded set-wide, apply
`mcp-nixos.overlays.fastmcp4` in addition.

## Development

```bash
nix develop          # Enter dev shell
nix build            # Build package
pytest tests/        # Run tests
ruff check .         # Lint
ruff format .        # Format
mypy mcp_nixos/      # Type check
```

## Acknowledgments

- **[NixHub.io](https://www.nixhub.io)** - Package version history
- **[search.nixos.org](https://search.nixos.org)** - Official NixOS search
- **[FlakeHub](https://flakehub.com)** - Flake registry by Determinate Systems
- **[Jetify](https://www.jetify.com)** - Creators of Devbox and NixHub
- **[Noogle](https://noogle.dev)** - Nix function search engine
- **[NuschtOS](https://github.com/NuschtOS/search)** - Static option search infrastructure powering Nixvim support
- **[Nixvim](https://github.com/nix-community/nixvim)** - Neovim configuration framework for Nix
- **[NVF](https://github.com/NotAShelf/nvf)** - Neovim configuration framework and published option catalogue

## License

MIT - Because sharing is caring.

---

*Created by James Brink. Maintained by mass̶o̶c̶h̶i̶s̶t̶s̶ enthusiasts who enjoy Nix.*