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

CodeRabbit Pull Request Reviews

Quick Start

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

Option 1: uvx (Recommended)

config.json

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

Option 2: Nix

config.json

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

Option 3: Docker

config.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 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:

config.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
NVF - 2.4K+ Neovim options from its published unstable documentation
FlakeHub - 600+ flakes from FlakeHub.com registry
Noogle - 2K+ Nix functions with type signatures via noogle.dev
NixOS Wiki - Community documentation and guides from wiki.nixos.org
nix.dev - Official Nix tutorials and guides from nix.dev
Package versions - Historical versions with commit hashes via 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:

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:

server.ts

# 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 - Package version history
search.nixos.org - Official NixOS search
FlakeHub - Flake registry by Determinate Systems
Jetify - Creators of Devbox and NixHub
Noogle - Nix function search engine
NuschtOS - Static option search infrastructure powering Nixvim support
Nixvim - Neovim configuration framework for Nix
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.

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

Quick Start

Option 1: uvx (Recommended)

Option 2: Nix

Option 3: Docker

Option 4: HTTP (Remote MCP)

Option 5: Pi Coding Agent

What Is This?

The Tools

nix - Unified Query Tool

nix_versions - Package Version History

Installation

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

Development

Acknowledgments

License

`nix` - Unified Query Tool

`nix_versions` - Package Version History