Support declarative nix installation

[Malix-Labs]

Context

There is no documented declarative Nix installation methods (configuration.nix, flake.nix, home.nix)

mcp-nixos/README.md

Lines 110 to 117 in f4c6065

	### For Nix Users (You Know Who You Are)
	```bash
	# Run without installing
	nix run github:utensils/mcp-nixos
	# Install to profile
	nix profile install github:utensils/mcp-nixos
	```

Problem

Installing packages declaratively is one of the key feature of Nix

Most Nix users never use imperative installation methods such as nix profile install for global or user scoped install

Solution

Feature a documentation for a declarative nix installation method

[Malix-Labs]

Find all the different ways of installing mcp-nixos declaratively

Maybe the flake.nix we have in this repo is to be enhanced

References

• docs: Add examples and declarative usage #47

[jeanlucthumm]

https://github.com/jeanlucthumm/dotfiles/blob/4d466349170cf034db08da05adab3bc9884f984b/nix/home/modules/llm.nix#L8

it's available in nixpkgs, so isn't it the exact same declaration method as any other nixpkgs? I'm not sure extra documentation is needed

https://search.nixos.org/packages?channel=unstable&query=mcp-nixos

[Malix-Labs]

Indeed @jeanlucthumm!

I was not aware of that because it isn't showing up for 25.05

Have you succeeded installing mcp-nixos from flakes?

[jeanlucthumm]

@Malix-Labs Do you mean by adding your flake as an input? No, I've just relied on the packaged version.

[Malix-Labs]

Okay

I personally succeeded using the flake as an input but it's cumbersome

I will try to see if there are ways to improve that from updating our flake.nix file

[jeanlucthumm]

Hmmm doesn't your flake have this:

mcp-nixos/flake.nix

Lines 129 to 133 in 46b4d4d

	# Packages
	packages = {
	default = pythonPackage;
	mcp-nixos = pythonPackage;
	};

So it should be relatively straight forward? I use the same pattern for one of my projects here:

https://github.com/jeanlucthumm/reddit-easy-post/blob/ae154d7dd0d0e4280939cd062ca8367a2fb92b1e/flake.nix#L104-L107

And then it's super super easy to just add it as an overlay in my dotfiles:

https://github.com/jeanlucthumm/dotfiles/blob/3798e816c58a6cd7c194743d55cc072573e59073/nix/overlays/default.nix#L13

Called by e.g.: https://github.com/jeanlucthumm/dotfiles/blob/3798e816c58a6cd7c194743d55cc072573e59073/nix/flake.nix#L106

TBF I might be underestimating how straight forward this is for someone that's new to nix