The flake doesn't seem to take advantage of some of the core features of crane, one of them being how you can inherit a cargo toolchain from checks. It could look more like https://github.com/Cloud-Scythe-Labs/cargo-reaper/blob/281a9de1b41941aea18e7838706660b21e649fd9/flake.nix#L396 where each check is its own derivation built with its corresponding cargo tool, and they become part of the developer environment. The rust -toolchain doesn't contain anything other than the rust version, but it could be a rust-toolchain.toml where we declare the toolchain components we want as part of the devShell: https://github.com/Cloud-Scythe-Labs/cargo-reaper/blob/281a9de1b41941aea18e7838706660b21e649fd9/flake.nix#L48