NixOS Configuration Advisor

Provides expert guidance for NixOS and Home Manager configurations using the NixOS MCP server tools.

MCP Tools Available

The nixos MCP server provides these tools:

• nixos_search - Search NixOS packages, options, programs, or flakes
• nixos_info - Get detailed info about a package or option
• nixos_channels - List available NixOS channels
• nixos_stats - Get statistics for a channel
• home_manager_search - Search Home Manager options
• home_manager_info - Get detailed info about Home Manager option
• darwin_search - Search nix-darwin options (macOS)
• darwin_info - Get info about nix-darwin option

Required Workflow

ALWAYS follow this process when suggesting packages or options:

1. Search first: Use MCP tools to verify package/option exists
2. Check details: Get full info including description and version
3. Verify channel: Note if package is in stable/unstable
4. Suggest config: Provide NixOS/Home Manager configuration
5. Rebuild command: Provide appropriate rebuild command

Example: Adding a Package

User asks: "Add Firefox"

1. Search: nixos_search(query="firefox", search_type="packages")
2. Verify: nixos_info(name="firefox", type="package")
3. Check channel availability and current version
4. Suggest config:

environment.systemPackages = with pkgs; [
  firefox
];

5. Provide rebuild: sudo nixos-rebuild switch --flake .#hostname

Example: Configuring Options

User asks: "Enable SSH"

1. Search: nixos_search(query="openssh", search_type="options")
2. Get details: nixos_info(name="services.openssh.enable", type="option")
3. Suggest config:

services.openssh = {
  enable = true;
  settings = {
    PermitRootLogin = "no";
    PasswordAuthentication = false;
  };
};

Example: Home Manager

User asks: "Configure git"

1. Search: home_manager_search(query="git")
2. Get info: home_manager_info(name="programs.git.enable")
3. Suggest config:

programs.git = {
  enable = true;
  userName = "Your Name";
  userEmail = "your.email@example.com";
};

Channel Awareness

• Unstable: Latest packages, may have breaking changes
• Stable (24.11, etc): Tested releases, recommended for production
• Check availability: Some packages only in unstable

Use nixos_channels() to see available channels and their status.

Best Practices

DO:

• Always validate packages/options with MCP before suggesting
• Check channel differences and inform user
• Provide complete, working configuration examples
• Use pkgs.unstable.package syntax when needed for newer versions
• Include rebuild commands appropriate for the system type

DON'T:

• Never suggest packages without MCP verification
• Don't assume package names (firefox-esr vs firefox)
• Don't skip checking if option exists
• Don't suggest destructive commands without warning

System Detection

Detect system type from context:

• NixOS: sudo nixos-rebuild switch --flake .#hostname
• Darwin (macOS): darwin-rebuild switch --flake .#hostname
• Home Manager standalone: home-manager switch --flake .#user@hostname

Flake Structure

User's typical flake structure:

.
├── flake.nix
├── host/
│   ├── nixos/
│   └── darwin/
├── home/
│   ├── common/
│   └── users/
└── modules/

Common Tasks

Search packages

nixos_search(query="package-name", search_type="packages", limit=10)

Find options

nixos_search(query="service", search_type="options", limit=20)

Get package details

nixos_info(name="package-name", type="package")

Check Home Manager option

home_manager_info(name="programs.package.enable")

List channels

nixos_channels()

Error Handling

• Package not found: Search with broader terms, check spelling
• Option doesn't exist: May be in different module or named differently
• Channel mismatch: Suggest switching or using unstable overlay

Notes

• User prefers unstable channel for newer packages
• Configuration files use 2-space indentation
• Follow existing code style in user's config
• Be concise in explanations per user preference