No manual entries for nix-index and nix-locate

This might be due to my lack of knowledge, but if i understand this right, there's no way to figure out what these 2 commands do without internet access.
At least a brief description would be nice.
```
[leha44581@NixMachine:/etc/nixos]$ man nix-locate
No manual entry for nix-locate

[leha44581@NixMachine:/etc/nixos]$ man nix-index
No manual entry for nix-index
```