Add note for nixtamal in home-manager / other configs in README.md

README.md

@@ -130,8 +130,33 @@ in
 }
 ```
 
-If your configuration already provides `pkgs`, reuse it instead of importing Nixpkgs again. For
-NixOS or nix-darwin, select the corresponding module just as in the flake examples above:
+If your configuration already has a package set available independently of module arguments, pass
+it as `pkgs` to reuse its Nixpkgs configuration and overlays.
+
+Home Manager's usual `pkgs` module argument cannot be used to calculate that module's `imports`; it
+is provided through the module graph after imports are collected. When your pinned inputs are
+available through `home-manager.extraSpecialArgs`, pass the pinned Nixpkgs source instead. With
+[Nixtamal](https://nixtamal.toast.al/):
+
+```nix
+# `nixtamal` is provided through `home-manager.extraSpecialArgs`.
+{ nixtamal, ... }:
+
+let
+  nixcord = import nixtamal.nixcord {
+    nixpkgs = nixtamal.nixpkgs;
+  };
+in
+{
+  imports = [ nixcord.homeModules.nixcord ];
+}
+```
+
+This gives `nixcord.packages` a separate package set from the supplied Nixpkgs source; it does not
+inherit the Home Manager package set's configuration or overlays. An empty argument set also works,
+but uses Nixcord's bundled Nixpkgs pin for package outputs.
+
+For NixOS or nix-darwin, select the corresponding module just as in the flake examples above:
 
 ```nix
 # NixOS