basic interface and no success trying to use them in a Tool script

scenes/spawners/Spawner.cs

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+using Godot;
+using System;
+
+[Tool]
+public partial class Spawner : Node3D
+{
+	[Export(PropertyHint.NodeType)]
+	public PackedScene SceneToSpawn { get; set; }
+	
+	[Export]
+	public Resource Inputs;
+	[Export]
+	public Node3D Target { get; set; }
+	
+	[Export(PropertyHint.Range, "0.1, 100, 0.1, or_greater")]
+	public float SpawnInterval { get; set; } = 1.0f;
+	[Export]
+	public bool IsActiveOnStart { get; set; } = true;
+	
+	private float _spawnTimer;
+	private bool _isActive;
+	
+	public override void _Ready()
+	{
+		_isActive = IsActiveOnStart && !Engine.IsEditorHint();  // Keep it inactive in Editor
+		_spawnTimer = SpawnInterval;
+	}
+
+	public override void _Process(double delta)
+	{
+		if (!_isActive) return;
+		
+		_spawnTimer -= (float) delta;
+		if (_spawnTimer <= 0) Spawn(); 
+	}
+
+	public void Spawn()
+	{
+		if (SceneToSpawn == null || !SceneToSpawn.CanInstantiate()) return;
+		
+		var spawnedInstance = SceneToSpawn.Instantiate() as FirstEnemy;
+		if (spawnedInstance == null) return;
+		
+		spawnedInstance.Inputs = Inputs as EnemyInitInputs;
+		spawnedInstance.Target = Target;
+		GetTree().GetCurrentScene().AddChild(spawnedInstance);
+		spawnedInstance.GlobalPosition = GlobalPosition;
+		
+		_spawnTimer = SpawnInterval;
+	}
+	
+	public void StartSpawning()
+	{
+		_isActive = true;
+		_spawnTimer = SpawnInterval;
+	}
+	
+	public void StopSpawning()
+	{
+		_isActive = false;
+	}
+}

scenes/spawners/Spawner.cs.uid

@@ -0,0 +1 @@
+uid://djyspwixi01j5

scenes/spawners/spawner.tscn

@@ -0,0 +1,10 @@
+[gd_scene load_steps=3 format=3 uid="uid://c305mfrtumcyq"]
+
+[ext_resource type="Script" uid="uid://djyspwixi01j5" path="res://scenes/spawners/Spawner.cs" id="1_2otbo"]
+[ext_resource type="PackedScene" uid="uid://dxt0e2ugmttqq" path="res://scenes/enemies/first_enemy.tscn" id="2_2otbo"]
+
+[node name="Spawner" type="Node3D"]
+script = ExtResource("1_2otbo")
+SceneToSpawn = ExtResource("2_2otbo")
+
+[node name="Marker3D" type="Marker3D" parent="."]