added tooltips and notes to asset sources

com.unity.perception/Editor/Randomization/Uxml/AssetSource/AssetSourceElement.uxml

         <Label name="name" text="Field Name" class="unity-base-field__label"/>
         <VisualElement style="margin-left: 18px;">
             <VisualElement style="flex-direction: row; align-items: center;">
-                <Label text="Archetype" class="unity-base-field__label"/>
-                <editor:ToolbarMenu name="archetype-dropdown" text="Type" class="sampler__type-menu"/>
+                <Label
+                    text="Location"
+                    class="unity-base-field__label"
+                    tooltip="The asset source location to load assets from"/>
+                <editor:ToolbarMenu name="location-dropdown" text="Type" class="sampler__type-menu"/>
+            </VisualElement>
+            <VisualElement style="margin-left: 18px;">
+                <VisualElement name="fields-container" style="flex-grow: 1;"/>
+                <TextElement name="location-notes" class="scenario__info-box"/>
-                <Label text="Location" class="unity-base-field__label"/>
-                <editor:ToolbarMenu name="location-dropdown" text="Type" class="sampler__type-menu"/>
+                <Label
+                    text="Archetype"
+                    class="unity-base-field__label"
+                    tooltip="Archetypes preprocess assets loaded from the selected asset source location"/>
+                <editor:ToolbarMenu name="archetype-dropdown" text="Type" class="sampler__type-menu"/>
-            <VisualElement name="fields-container" style="flex-grow: 1;"/>
         </VisualElement>
     </VisualElement>
 </UXML>

com.unity.perception/Editor/Randomization/VisualElements/AssetSource/AssetSourceElement.cs

         ToolbarMenu m_ArchetypeToolbarMenu;
         ToolbarMenu m_LocationToolbarMenu;
         VisualElement m_FieldsContainer;
+        TextElement m_LocationNotes;
         Type m_AssetType;
 
         ArchetypeBase archetype =>
             var template = AssetDatabase.LoadAssetAtPath<VisualTreeAsset>(
                 $"{StaticData.uxmlDir}/AssetSource/AssetSourceElement.uxml");
             template.CloneTree(this);
-
-            if (assetSourceLocation == null)
-                CreateAssetSourceLocation(typeof(LocalAssetSourceLocation));
 
             var nameLabel = this.Q<Label>("name");
             nameLabel.text = property.displayName;
                     a => DropdownMenuAction.Status.Normal);
             }
 
+            m_LocationNotes = this.Q<TextElement>("location-notes");
-            m_LocationToolbarMenu.text = GetDisplayName(assetSourceLocation.GetType());
             foreach (var type in StaticData.assetSourceLocationTypes)
             {
                 m_LocationToolbarMenu.menu.AppendAction(
             }
-
-            CreatePropertyFields();
-        }
-
-        void ReplaceLocation(Type type)
-        {
-            CreateAssetSourceLocation(type);
-            m_LocationToolbarMenu.text = GetDisplayName(type);
-            CreatePropertyFields();
+            if (assetSourceLocation == null)
+                CreateAssetSourceLocation(typeof(LocalAssetSourceLocation));
+            UpdateLocationUI(assetSourceLocation.GetType());
         }
 
         void ReplaceArchetype(Type type)
             var newLocation = (AssetSourceLocation)Activator.CreateInstance(type);
             m_LocationProperty.managedReferenceValue = newLocation;
             m_LocationProperty.serializedObject.ApplyModifiedProperties();
+        }
+
+        void ReplaceLocation(Type type)
+        {
+            CreateAssetSourceLocation(type);
+            UpdateLocationUI(type);
+        }
+
+        void UpdateLocationUI(Type type)
+        {
+            m_LocationToolbarMenu.text = GetDisplayName(type);
+            var notesAttribute = (AssetSourceLocationNotes)Attribute.GetCustomAttribute(type, typeof(AssetSourceLocationNotes));
+            if (notesAttribute != null)
+            {
+                m_LocationNotes.text = notesAttribute.notes;
+                m_LocationNotes.style.display = new StyleEnum<DisplayStyle>(DisplayStyle.Flex);
+            }
+            else
+            {
+                m_LocationNotes.style.display = new StyleEnum<DisplayStyle>(DisplayStyle.None);
+            }
+            CreatePropertyFields();
         }
 
         void CreatePropertyFields()

com.unity.perception/Runtime/Randomization/Randomizers/AssetSources/AssetSourceLocationNotes.cs

+using System;
+
+namespace UnityEngine.Perception.Randomization
+{
+    /// <summary>
+    /// Used to annotate an AssetSourceLocation with notes within the inspector UI
+    /// </summary>
+    public class AssetSourceLocationNotes : Attribute
+    {
+        /// <summary>
+        /// The text notes to display in the AssetSourceLocation's UI.
+        /// </summary>
+        public string notes;
+
+        /// <summary>
+        /// Constructs a new AssetSourceLocationNotes attribute
+        /// </summary>
+        /// <param name="notes">The text notes to display in the inspector</param>
+        public AssetSourceLocationNotes(string notes)
+        {
+            this.notes = notes;
+        }
+    }
+}

com.unity.perception/Runtime/Randomization/Randomizers/AssetSources/AssetSourceLocationNotes.cs.meta

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