mcp-nixos MCP — Use Cases, Install & Live Demo

Why use it

Key features

130k+ NixOS packages + 23k+ system options queryable
Covers Home Manager (5k+ options), nix-darwin (1k+ macOS settings), Nixvim, FlakeHub, Noogle
nix_versions tool for historical versions + pinned nixpkgs commit hashes
No auth required — public API queries only
Runs via uvx, Nix flake, or Docker

Live Demo

What it looks like in practice

nixos.replay ▶ ready

0/0

Install

Pick your client

~/Library/Application Support/Claude/claude_desktop_config.json · Windows: %APPDATA%\Claude\claude_desktop_config.json

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

Open Claude Desktop → Settings → Developer → Edit Config. Restart after saving.

~/.cursor/mcp.json · .cursor/mcp.json

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

Cursor uses the same mcpServers schema as Claude Desktop. Project config wins over global.

VS Code → Cline → MCP Servers → Edit

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

Click the MCP Servers icon in the Cline sidebar, then "Edit Configuration".

~/.codeium/windsurf/mcp_config.json

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

Same shape as Claude Desktop. Restart Windsurf to pick up changes.

~/.continue/config.json

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

Continue uses an array of server objects rather than a map.

~/.config/zed/settings.json

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

Add to context_servers. Zed hot-reloads on save.

claude mcp add nixos -- uvx mcp-nixos

One-liner. Verify with claude mcp list. Remove with claude mcp remove.

Use Cases

Real-world ways to use mcp-nixos

Find a NixOS package by fuzzy name or purpose

👤 NixOS users, flake authors ⏱ ~5 min beginner

When to use: You remember roughly what the package does but not its nix attribute name.

Flow

Search

Find NixOS packages matching 'ocr command line tool'.✓ Copied

→ Ranked list of candidates with descriptions
Get details on the best fit

For tesseract, show me the attribute path, version in unstable vs 24.11, and which meta.platforms are supported.✓ Copied

→ Detail card with attr, versions, platforms

Outcome: The exact attribute to drop into your configuration.nix or flake.

Pitfalls

Channel mismatch — package only exists in unstable, not your stable channel — Ask explicitly about the channel you're on

Combine with: filesystem

Look up a NixOS module option with its type and default

👤 People writing NixOS modules ⏱ ~5 min beginner

When to use: You know there's an option 'somewhere' for enabling zswap and you don't want to grep nixpkgs.

Flow

Query options

Is there a NixOS option for enabling zswap? Show its type, default, and description.✓ Copied

→ Full option card
Get an example

Give me a minimal configuration.nix snippet that enables zswap with z3fold and 20% memory.✓ Copied

→ Copy-paste Nix snippet

Outcome: A correct option usage ready to paste in.

Pin nixpkgs to an old version of a package

👤 Users needing a specific older version ⏱ ~10 min intermediate

When to use: A newer version broke something and you want the last known-good commit.

Flow

Find historical versions

Show me past versions of nodejs_20 in nixpkgs with commit hashes.✓ Copied

→ Version→commit table
Generate a flake input

Generate the flake input pinning nodejs_20 20.15.0 from that commit.✓ Copied

→ Ready-to-paste flake.nix snippet

Outcome: A reproducibly pinned input for rollback.

Combine with: filesystem

Discover Home Manager options for a program

👤 Anyone using Home Manager ⏱ ~10 min beginner

When to use: You want to manage a program declaratively but aren't sure what options exist.

Flow

List program options

List every Home Manager option under programs.neovim.✓ Copied

→ Categorized option list
Build a minimal block

Give me a minimal programs.neovim block enabling Telescope and LSP for TS/Python.✓ Copied

→ Working HM snippet

Outcome: A working Home Manager config without reading the full manual.

Combinations

Pair with other MCPs for X10 leverage

nixos + filesystem

Find the option and write it into your config file

Find the NixOS option to enable flatpak, then add it to ~/nixos/configuration.nix with a comment.✓ Copied

nixos + github

Raise an issue when a package is missing

Is package foo-cli in nixpkgs? If not, open a github issue on our fork requesting it.✓ Copied

Tools

What this MCP exposes

Tool	Inputs	When to call	Cost
nix	action: search\|info\|stats\|options\|channels\|flake-inputs\|cache, args: ...	Any query over packages, options, channels	1 upstream API call
nix_versions	package: str	Need an older version / nixpkgs pin	1 upstream call

Cost & Limits

What this costs to run

API quota: Public APIs; generous limits but not infinite — don't hammer
Tokens per call: Options with descriptions: 500-2000 tokens. Lists can be larger.
Monetary: Free
Tip: Prefer info on one package over search returning 50.

Security

Permissions, secrets, blast radius

Credential storage: None

Data egress: Calls to search.nixos.org and related public APIs

Results reflect whatever upstream NixOS search returns — re-verify against your channel.
mcp-nixos does not run Nix; it does not execute any derivation.

Troubleshooting

Common errors and fixes

uvx not found

Install uv: curl -LsSf https://astral.sh/uv/install.sh | sh, then re-add the MCP.

Verify: uvx --version

No results for a package I know exists

Spelling varies in attribute names — try a looser query or search by description.

Verify: Retry with partial keyword

Stale version info

The MCP caches briefly; re-query in 5 minutes or pass action=cache to refresh.

Alternatives

mcp-nixos vs others

Alternative	When to use it instead	Tradeoff
search.nixos.org directly	You're fine with a browser tab	No AI in the loop
nix-search CLI	You want local fast search and have Nix installed	Needs local Nix + an up-to-date channel

More

Resources

📖 Read the official README on GitHub

🐙 Browse open issues

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