diff --git a/back/src/Kyoo.Abstractions/Models/LibraryItem.cs b/back/src/Kyoo.Abstractions/Models/Attributes/OneOf.cs
similarity index 55%
rename from back/src/Kyoo.Abstractions/Models/LibraryItem.cs
rename to back/src/Kyoo.Abstractions/Models/Attributes/OneOf.cs
index 14fc8aa0..de064603 100644
--- a/back/src/Kyoo.Abstractions/Models/LibraryItem.cs
+++ b/back/src/Kyoo.Abstractions/Models/Attributes/OneOf.cs
@@ -17,33 +17,17 @@
 // along with Kyoo. If not, see <https://www.gnu.org/licenses/>.
 
 using System;
-using System.Collections.Generic;
-using System.ComponentModel.DataAnnotations;
-using System.Text.Json.Serialization;
-using Kyoo.Utils;
 
-namespace Kyoo.Abstractions.Models
+namespace Kyoo.Abstractions.Models.Attributes;
+
+/// <summary>
+/// An attribute to inform that this interface is a type union
+/// </summary>
+[AttributeUsage(AttributeTargets.Interface)]
+public class OneOfAttribute : Attribute
 {
 	/// <summary>
-	/// The type of item, ether a show, a movie or a collection.
+	/// The types this union concist of.
 	/// </summary>
-	public enum ItemKind
-	{
-		/// <summary>
-		/// The <see cref="ILibraryItem"/> is a <see cref="Show"/>.
-		/// </summary>
-		Show,
-
-		/// <summary>
-		/// The <see cref="ILibraryItem"/> is a Movie.
-		/// </summary>
-		Movie,
-
-		/// <summary>
-		/// The <see cref="ILibraryItem"/> is a <see cref="Collection"/>.
-		/// </summary>
-		Collection
-	}
-
-	public interface ILibraryItem : IResource, IThumbnails, IMetadata, IAddedDate { }
+	public Type[] Types { get; set; }
 }
diff --git a/back/src/Kyoo.Abstractions/Models/ILibraryItem.cs b/back/src/Kyoo.Abstractions/Models/ILibraryItem.cs
new file mode 100644
index 00000000..bdeb61d5
--- /dev/null
+++ b/back/src/Kyoo.Abstractions/Models/ILibraryItem.cs
@@ -0,0 +1,27 @@
+// Kyoo - A portable and vast media library solution.
+// Copyright (c) Kyoo.
+//
+// See AUTHORS.md and LICENSE file in the project root for full license information.
+//
+// Kyoo is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// any later version.
+//
+// Kyoo is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Kyoo. If not, see <https://www.gnu.org/licenses/>.
+
+using Kyoo.Abstractions.Models.Attributes;
+
+namespace Kyoo.Abstractions.Models;
+
+/// <summary>
+/// A show, a movie or a collection.
+/// </summary>
+[OneOf(Types = new[] { typeof(Show), typeof(Movie), typeof(Collection) })]
+public interface ILibraryItem : IResource, IThumbnails, IMetadata, IAddedDate { }
diff --git a/back/src/Kyoo.Core/Controllers/Repositories/LibraryItemRepository.cs b/back/src/Kyoo.Core/Controllers/Repositories/LibraryItemRepository.cs
index f7e70dd1..0eac4667 100644
--- a/back/src/Kyoo.Core/Controllers/Repositories/LibraryItemRepository.cs
+++ b/back/src/Kyoo.Core/Controllers/Repositories/LibraryItemRepository.cs
@@ -98,7 +98,7 @@ namespace Kyoo.Core.Controllers
 				// TODO: Implement default sort by
 				Sort<T>.Default => $"coalesce({string.Join(", ", tables.Select(x => $"{x}.name"))})",
 				Sort<T>.By(string key, bool desc) => $"coalesce({string.Join(", ", tables.Select(x => $"{x}.{key}"))}) {(desc ? "desc" : "asc")}",
-				Sort<T>.Random(var seed) => $"md5({seed} || coalesce({string.Join(", ", tables.Select(x => $"{x}.id"))}))",
+				Sort<T>.Random(var seed) => $"md5('{seed}' || coalesce({string.Join(", ", tables.Select(x => $"{x}.id"))}))",
 				Sort<T>.Conglomerate(var list) => string.Join(", ", list.Select(x => ProcessSort(x, tables))),
 				_ => throw new SwitchExpressionException(),
 			};
diff --git a/back/src/Kyoo.Core/Views/Helper/Serializers/JsonSerializerContract.cs b/back/src/Kyoo.Core/Views/Helper/Serializers/JsonSerializerContract.cs
index d9ca24dc..a2e086e5 100644
--- a/back/src/Kyoo.Core/Views/Helper/Serializers/JsonSerializerContract.cs
+++ b/back/src/Kyoo.Core/Views/Helper/Serializers/JsonSerializerContract.cs
@@ -16,7 +16,9 @@
 // You should have received a copy of the GNU General Public License
 // along with Kyoo. If not, see <https://www.gnu.org/licenses/>.
 
+using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Reflection;
 using Kyoo.Abstractions.Models;
 using Kyoo.Abstractions.Models.Attributes;
@@ -58,8 +60,7 @@ namespace Kyoo.Core.Api
 			{
 				property.ShouldSerialize = _ =>
 				{
-					ICollection<string>? fields = (ICollection<string>)_httpContextAccessor.HttpContext!.Items["fields"]!;
-					if (fields == null)
+					if (_httpContextAccessor.HttpContext!.Items["fields"] is not ICollection<string> fields)
 						return false;
 					return fields.Contains(member.Name);
 				};
@@ -71,5 +72,43 @@ namespace Kyoo.Core.Api
 				property.ShouldDeserialize = _ => false;
 			return property;
 		}
+
+		protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
+		{
+			IList<JsonProperty> properties = base.CreateProperties(type, memberSerialization);
+
+			if (properties.All(x => x.PropertyName != "kind"))
+			{
+				properties.Add(new JsonProperty()
+				{
+					DeclaringType = type,
+					PropertyName = "kind",
+					UnderlyingName = "kind",
+					PropertyType = typeof(string),
+					ValueProvider = new FixedValueProvider(type.Name),
+					Readable = true,
+					Writable = false,
+					TypeNameHandling = TypeNameHandling.None,
+				});
+			}
+
+			return properties;
+		}
+
+		public class FixedValueProvider : IValueProvider
+		{
+			private readonly object _value;
+
+			public FixedValueProvider(object value)
+			{
+				_value = value;
+			}
+
+			public object GetValue(object target)
+				=> _value;
+
+			public void SetValue(object target, object? value)
+				=> throw new NotImplementedException();
+		}
 	}
 }