mcp-nixos

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

Quick Start

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

Option 1: uvx (Recommended)

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

Option 2: Nix

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

Option 3: Docker

{
  "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).

# 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):

MCP_NIXOS_TRANSPORT=stdio mcp-nixos

Custom path:

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

Stateless HTTP (disables per-client session state):

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):

pi install npm:pi-mcp-adapter

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

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:

# 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

nix_versions(package, version, limit)

Examples:

# 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.

# Run directly (no install)
uvx mcp-nixos

# Or install
pip install mcp-nixos

For Nix users:

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:

# 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:

# 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

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.