diff --git a/bin/jadb.dart b/bin/jadb.dart
index 5da6b22..214e133 100644
--- a/bin/jadb.dart
+++ b/bin/jadb.dart
@@ -27,7 +27,7 @@ void addJadbArg(ArgParser argParser) {
     abbr: 'f',
     help: 'Path to the SQLite database file.',
     valueHelp: 'PATH',
-    mandatory: true,
+    defaultsTo: Platform.environment['JADB_PATH'],
   );
 }
 
@@ -75,7 +75,7 @@ class QueryKanji extends Command {
 
   Future<void> run() async {
     if (argResults!.option('libsqlite') == null ||
-        !argResults!.wasParsed('jadb')) {
+        argResults!.option('jadb') == null) {
       print(argParser.usage);
       exit(64);
     }
@@ -115,7 +115,7 @@ class QueryWord extends Command {
 
   Future<void> run() async {
     if (argResults!.option('libsqlite') == null ||
-        !argResults!.wasParsed('jadb')) {
+        argResults!.option('jadb') == null) {
       print(argParser.usage);
       exit(64);
     }
diff --git a/flake.nix b/flake.nix
index 924f425..9a3423b 100644
--- a/flake.nix
+++ b/flake.nix
@@ -46,13 +46,32 @@
     forAllSystems = f: lib.genAttrs systems (system: f system nixpkgs.legacyPackages.${system});
   in {
     apps = forAllSystems (system: pkgs: {
-      default = let
-        inherit (self.packages.${system}) docs;
-      in {
+      default = {
         type = "app";
-        program = "${pkgs.writeShellScript "host-docs" ''
-          ${pkgs.python3} -m http.server -d ${docs}
-        ''}";
+        program = let
+          script = pkgs.writeShellApplication {
+            name = "jadb-tool";
+
+            runtimeEnv = {
+              JADB_PATH = "${self.packages.${system}.database}/jadb.sqlite";
+              LIBSQLITE_PATH = "${pkgs.sqlite.out}/lib/libsqlite3.so";
+            };
+
+            text = ''
+              ${lib.getExe self.packages.${system}.database-tool} "$@"
+            '';
+          };
+        in lib.getExe script;
+      };
+
+      docs = {
+        type = "app";
+        program = let
+          inherit (self.packages.${system}) docs;
+          script = pkgs.writeShellScript "host-docs" ''
+            ${pkgs.python3} -m http.server -d ${docs}
+          '';
+        in "${script}";
       };
     });
 
@@ -68,6 +87,7 @@
         ];
         env = {
           LIBSQLITE_PATH = "${pkgs.sqlite.out}/lib/libsqlite3.so";
+          JADB_PATH = "result/jadb.sqlite";
         };
       };
     });