diff --git a/nuget-dotnetcli/dotnet-typegen.nuspec b/nuget-dotnetcli/dotnet-typegen.nuspec
index 27d58977..cb1feb7e 100644
--- a/nuget-dotnetcli/dotnet-typegen.nuspec
+++ b/nuget-dotnetcli/dotnet-typegen.nuspec
@@ -2,7 +2,7 @@
 <package>
   <metadata>
     <id>dotnet-typegen</id>
-    <version>5.0.0</version>
+    <version>5.0.1</version>
     <authors>Jacek Burzynski</authors>
     <owners>Jacek Burzynski</owners>
     <license type="file">LICENSE</license>
diff --git a/nuget/TypeGen.nuspec b/nuget/TypeGen.nuspec
index 235048a9..d6fe7c08 100644
--- a/nuget/TypeGen.nuspec
+++ b/nuget/TypeGen.nuspec
@@ -2,7 +2,7 @@
 <package>
   <metadata>
     <id>TypeGen</id>
-    <version>5.0.0</version>
+    <version>5.0.1</version>
     <authors>Jacek Burzynski</authors>
     <owners>Jacek Burzynski</owners>
     <license type="file">LICENSE</license>
diff --git a/src/TypeGen/TypeGen.Cli/ApplicationConfig.cs b/src/TypeGen/TypeGen.Cli/ApplicationConfig.cs
index 3f411074..3399433e 100644
--- a/src/TypeGen/TypeGen.Cli/ApplicationConfig.cs
+++ b/src/TypeGen/TypeGen.Cli/ApplicationConfig.cs
@@ -2,5 +2,5 @@ namespace TypeGen.Cli;
 
 internal class ApplicationConfig
 {
-    public const string Version = "5.0.0";
+    public const string Version = "5.0.1";
 }
diff --git a/src/TypeGen/TypeGen.Cli/TypeGen.Cli.csproj b/src/TypeGen/TypeGen.Cli/TypeGen.Cli.csproj
index 85b97bff..39013f9c 100644
--- a/src/TypeGen/TypeGen.Cli/TypeGen.Cli.csproj
+++ b/src/TypeGen/TypeGen.Cli/TypeGen.Cli.csproj
@@ -2,9 +2,9 @@
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <TargetFramework>net8.0</TargetFramework>
-    <AssemblyVersion>5.0.0.0</AssemblyVersion>
-    <FileVersion>5.0.0.0</FileVersion>
-    <Version>5.0.0</Version>
+    <AssemblyVersion>5.0.0.1</AssemblyVersion>
+    <FileVersion>5.0.0.1</FileVersion>
+    <Version>5.0.1</Version>
     <PackageId>TypeGen</PackageId>
     <Authors />
   </PropertyGroup>
diff --git a/src/TypeGen/TypeGen.Core/Generator/Generator.cs b/src/TypeGen/TypeGen.Core/Generator/Generator.cs
index 35b56a69..9504f445 100644
--- a/src/TypeGen/TypeGen.Core/Generator/Generator.cs
+++ b/src/TypeGen/TypeGen.Core/Generator/Generator.cs
@@ -1,5 +1,4 @@
 using System;
-using System.Collections;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
@@ -12,6 +11,7 @@
 using TypeGen.Core.Logging;
 using TypeGen.Core.Metadata;
 using TypeGen.Core.SpecGeneration;
+using TypeGen.Core.SpecGeneration.Builders.Traits;
 using TypeGen.Core.Storage;
 using TypeGen.Core.TypeAnnotations;
 using TypeGen.Core.Validation;
@@ -65,8 +65,8 @@ public Generator(GeneratorOptions options, ILogger logger = null)
             _typeService = new TypeService(_metadataReaderFactory, generatorOptionsProvider);
             _typeDependencyService = new TypeDependencyService(_typeService, _metadataReaderFactory, generatorOptionsProvider);
             _templateService = new TemplateService(internalStorage, generatorOptionsProvider);
-
             _tsContentGenerator = new TsContentGenerator(_typeDependencyService,
+
                 _typeService,
                 _templateService,
                 new TsContentParser(_fileSystem),
@@ -140,6 +140,7 @@ public IEnumerable<string> Generate(IEnumerable<GenerationSpec> generationSpecs)
             Requires.NotNullOrEmpty(generationSpecs, nameof(generationSpecs));
 
             generationSpecs = generationSpecs.ToList();
+
             var files = new List<string>();
             _generationContext = new GenerationContext(_fileSystem);
             
@@ -153,7 +154,7 @@ public IEnumerable<string> Generate(IEnumerable<GenerationSpec> generationSpecs)
                 _metadataReaderFactory.GenerationSpec = generationSpec;
                 
                 foreach (KeyValuePair<Type, TypeSpec> kvp in generationSpec.TypeSpecs)
-                    files.AddRange(GenerateMarkedType(kvp.Key));
+                    files.AddRange(GenerateMarkedType(kvp.Key, kvp.Value));
             }
             
             files = files.Distinct().ToList();
@@ -326,7 +327,7 @@ private IEnumerable<string> GenerateIndexFile(IEnumerable<string> generatedFiles
             return new[] { filename };
         }
         
-        private IEnumerable<string> GenerateMarkedType(Type type)
+        private IEnumerable<string> GenerateMarkedType(Type type, TypeSpec typeSpec)
         {
             if (Options.IsTypeBlacklisted(type)) return Enumerable.Empty<string>();
             
@@ -334,7 +335,7 @@ private IEnumerable<string> GenerateMarkedType(Type type)
             
             _generationContext.BeginTypeGeneration(type);
             _generationContext.AddGeneratedType(type);
-            ExecuteWithTypeContextLogging(() => { files = GenerateType(type); });
+            ExecuteWithTypeContextLogging(() => { files = GenerateType(type, typeSpec); });
             _generationContext.EndTypeGeneration();
 
             return files.Distinct();
@@ -346,7 +347,7 @@ private IEnumerable<string> GenerateMarkedType(Type type)
         /// </summary>
         /// <param name="type"></param>
         /// <returns>Generated TypeScript file paths (relative to the Options.BaseOutputDirectory)</returns>
-        private IEnumerable<string> GenerateType(Type type)
+        private IEnumerable<string> GenerateType(Type type, TypeSpec typeSpec)
         {
             var classAttribute = _metadataReaderFactory.GetInstance().GetAttribute<ExportTsClassAttribute>(type);
             var interfaceAttribute = _metadataReaderFactory.GetInstance().GetAttribute<ExportTsInterfaceAttribute>(type);
@@ -354,12 +355,12 @@ private IEnumerable<string> GenerateType(Type type)
 
             if (classAttribute != null)
             {
-                return GenerateClass(type, classAttribute);
+                return GenerateClass(type, classAttribute, typeSpec);
             }
 
             if (interfaceAttribute != null)
             {
-                return GenerateInterface(type, interfaceAttribute);
+                return GenerateInterface(type, interfaceAttribute, typeSpec);
             }
 
             if (enumAttribute != null)
@@ -367,16 +368,17 @@ private IEnumerable<string> GenerateType(Type type)
                 return GenerateEnum(type, enumAttribute);
             }
 
-            return GenerateNotMarkedType(type, Options.BaseOutputDirectory);
+            return GenerateNotMarkedType(type, Options.BaseOutputDirectory, typeSpec);
         }
-        
+
         /// <summary>
         /// Generates TypeScript files for types that are not marked with an ExportTs... attribute
         /// </summary>
         /// <param name="type"></param>
         /// <param name="outputDirectory"></param>
+        /// <param name="typeSpec"></param>
         /// <returns>Generated TypeScript file paths (relative to the Options.BaseOutputDirectory)</returns>
-        private IEnumerable<string> GenerateNotMarkedType(Type type, string outputDirectory)
+        private IEnumerable<string> GenerateNotMarkedType(Type type, string outputDirectory, TypeSpec typeSpec)
         {
             if (Options.IsTypeBlacklisted(type)) return Enumerable.Empty<string>();
             
@@ -384,12 +386,12 @@ private IEnumerable<string> GenerateNotMarkedType(Type type, string outputDirect
             if (typeInfo.IsClass || typeInfo.IsStruct())
             {
                 return Options.ExportTypesAsInterfacesByDefault
-                    ? GenerateInterface(type, new ExportTsInterfaceAttribute { OutputDir = outputDirectory })
-                    : GenerateClass(type, new ExportTsClassAttribute { OutputDir = outputDirectory });
+                    ? GenerateInterface(type, new ExportTsInterfaceAttribute { OutputDir = outputDirectory }, typeSpec)
+                    : GenerateClass(type, new ExportTsClassAttribute { OutputDir = outputDirectory }, typeSpec);
             }
             
             if (typeInfo.IsInterface)
-                return GenerateInterface(type, new ExportTsInterfaceAttribute { OutputDir = outputDirectory });
+                return GenerateInterface(type, new ExportTsInterfaceAttribute { OutputDir = outputDirectory }, typeSpec);
 
             if (typeInfo.IsEnum)
                 return GenerateEnum(type, new ExportTsEnumAttribute { OutputDir = outputDirectory });
@@ -402,11 +404,12 @@ private IEnumerable<string> GenerateNotMarkedType(Type type, string outputDirect
         /// </summary>
         /// <param name="type"></param>
         /// <param name="classAttribute"></param>
+        /// <param name="typeSpec"></param>
         /// <returns>Generated TypeScript file paths (relative to the Options.BaseOutputDirectory)</returns>
-        private IEnumerable<string> GenerateClass(Type type, ExportTsClassAttribute classAttribute)
+        private IEnumerable<string> GenerateClass(Type type, ExportTsClassAttribute classAttribute, TypeSpec typeSpec)
         {
             string outputDir = classAttribute.OutputDir;
-            IEnumerable<string> dependenciesGenerationResult = GenerateTypeDependencies(type, outputDir);
+            IEnumerable<string> dependenciesGenerationResult = GenerateTypeDependencies(type, outputDir, typeSpec);
 
             // get text for sections
 
@@ -428,7 +431,7 @@ private IEnumerable<string> GenerateClass(Type type, ExportTsClassAttribute clas
             }
 
             string importsText = _tsContentGenerator.GetImportsText(type, outputDir);
-            string propertiesText = GetClassPropertiesText(type);
+            string propertiesText = GetClassPropertiesText(type, typeSpec.AdditionalClassProperties);
 
             // generate the file content
 
@@ -458,11 +461,12 @@ private IEnumerable<string> GenerateClass(Type type, ExportTsClassAttribute clas
         /// </summary>
         /// <param name="type"></param>
         /// <param name="interfaceAttribute"></param>
+        /// <param name="typeSpec"></param>
         /// <returns>Generated TypeScript file paths (relative to the Options.BaseOutputDirectory)</returns>
-        private IEnumerable<string> GenerateInterface(Type type, ExportTsInterfaceAttribute interfaceAttribute)
+        private IEnumerable<string> GenerateInterface(Type type, ExportTsInterfaceAttribute interfaceAttribute, TypeSpec typeSpec)
         {
             string outputDir = interfaceAttribute.OutputDir;
-            IEnumerable<string> dependenciesGenerationResult = GenerateTypeDependencies(type, outputDir);
+            IEnumerable<string> dependenciesGenerationResult = GenerateTypeDependencies(type, outputDir, typeSpec);
 
             // get text for sections
 
@@ -648,20 +652,44 @@ private void LogClassPropertyWarnings(MemberInfo memberInfo)
         /// Gets TypeScript class properties definition source code
         /// </summary>
         /// <param name="type"></param>
+        /// <param name="additionalProperties"></param>
         /// <returns></returns>
-        private string GetClassPropertiesText(Type type)
+        private string GetClassPropertiesText(Type type, IEnumerable<AdditionalClassProperty> additionalProperties)
         {
             var propertiesText = "";
             IEnumerable<MemberInfo> memberInfos = type.GetTsExportableMembers(_metadataReaderFactory.GetInstance());
 
-            // create TypeScript source code for properties' definition
-
+            // Generate TypeScript properties from C# members
             propertiesText += memberInfos
-                .Aggregate(propertiesText, (current, memberInfo) => current + GetClassPropertyText(type, memberInfo));
+                .Aggregate("", (current, memberInfo) => current + GetClassPropertyText(type, memberInfo));
+
+            propertiesText += GetAdditionalPropertiesText(additionalProperties);
 
             return RemoveLastLineEnding(propertiesText);
         }
 
+        /// <summary>
+        /// Gets TypeScript class additional properties if defined
+        /// </summary>
+        /// <param name="additionalProperties"></param>
+        /// <returns></returns>
+        private string GetAdditionalPropertiesText(IEnumerable<AdditionalClassProperty> additionalProperties)
+        {
+            if (!additionalProperties.Any())
+            {
+                return "";
+            }
+
+            var additionalPropertiesText = _templateService.FillWithSingleLineComment("Additional properties");
+
+            foreach (var property in additionalProperties)
+            {
+                additionalPropertiesText += _templateService.FillClassPropertyTemplate(property.Name, property.Type, property.DefaultValue);
+            }
+
+            return additionalPropertiesText;
+        }
+
         /// <summary>
         /// Gets TypeScript interface property definition source code
         /// </summary>
@@ -772,8 +800,9 @@ private string GetEnumMembersText(Type type, bool asUnionType)
         /// </summary>
         /// <param name="type"></param>
         /// <param name="outputDir"></param>
+        /// <param name="typeSpec"></param>
         /// <returns>Generated TypeScript file paths (relative to the Options.BaseOutputDirectory)</returns>
-        private IEnumerable<string> GenerateTypeDependencies(Type type, string outputDir)
+        private IEnumerable<string> GenerateTypeDependencies(Type type, string outputDir, TypeSpec typeSpec)
         {
             var generatedFiles = new List<string>();
             var typeDependencies = _typeDependencyService.GetTypeDependencies(type);
@@ -793,7 +822,7 @@ private IEnumerable<string> GenerateTypeDependencies(Type type, string outputDir
                 
                 try
                 {
-                    generatedFiles.AddRange(GenerateNotMarkedType(typeDependency, defaultOutputDir));
+                    generatedFiles.AddRange(GenerateNotMarkedType(typeDependency, defaultOutputDir, typeSpec));
                 }
                 catch (Exception ex)
                 {
diff --git a/src/TypeGen/TypeGen.Core/Generator/Services/ITemplateService.cs b/src/TypeGen/TypeGen.Core/Generator/Services/ITemplateService.cs
index d196ffd1..fd35f38e 100644
--- a/src/TypeGen/TypeGen.Core/Generator/Services/ITemplateService.cs
+++ b/src/TypeGen/TypeGen.Core/Generator/Services/ITemplateService.cs
@@ -7,6 +7,7 @@ internal interface ITemplateService
         string FillClassTemplate(string imports, string name, string extends, string implements, string properties, string tsDoc, string customHead, string customBody, string fileHeading = null);
         string FillClassDefaultExportTemplate(string imports, string name, string exportName, string extends, string implements, string properties, string tsDoc, string customHead, string customBody, string fileHeading = null);
         string FillClassPropertyTemplate(string modifiers, string name, string type, IEnumerable<string> typeUnions, bool isOptional, string tsDoc, string defaultValue = null);
+        string FillClassPropertyTemplate(string name, string type, string defaultValue = null);
         string FillInterfaceTemplate(string imports, string name, string extends, string properties, string tsDoc, string customHead, string customBody, string fileHeading = null);
         string FillInterfaceDefaultExportTemplate(string imports, string name, string exportName, string extends, string properties, string tsDoc, string customHead, string customBody, string fileHeading = null);
         string FillInterfacePropertyTemplate(string modifiers, string name, string type, IEnumerable<string> typeUnions, bool isOptional, string tsDoc);
@@ -17,6 +18,7 @@ internal interface ITemplateService
         string FillImportTemplate(string name, string typeAlias, string path, bool useImportType);
         string FillImportDefaultExportTemplate(string name, string path, bool useImportType);
         string FillIndexTemplate(string exports);
+        string FillWithSingleLineComment(string comment);
         string FillIndexExportTemplate(string filename);
         string GetExtendsText(string name);
         string GetExtendsText(IEnumerable<string> names);
diff --git a/src/TypeGen/TypeGen.Core/Generator/Services/TemplateService.cs b/src/TypeGen/TypeGen.Core/Generator/Services/TemplateService.cs
index 3ca1759e..568c86e9 100644
--- a/src/TypeGen/TypeGen.Core/Generator/Services/TemplateService.cs
+++ b/src/TypeGen/TypeGen.Core/Generator/Services/TemplateService.cs
@@ -1,6 +1,8 @@
 using System.Collections;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
+using System.Xml.Linq;
 using TypeGen.Core.Storage;
 using TypeGen.Core.Utils;
 
@@ -33,6 +35,8 @@ internal class TemplateService : ITemplateService
         private readonly string _indexTemplate;
         private readonly string _indexExportTemplate;
         private readonly string _headingTemplate;
+        private readonly string _singleLineCommentTemplate;
+        private readonly string _lineBreakTemplate;
 
         private GeneratorOptions GeneratorOptions => _generatorOptionsProvider.GeneratorOptions;
 
@@ -58,6 +62,8 @@ public TemplateService(IInternalStorage internalStorage, IGeneratorOptionsProvid
             _indexTemplate = _internalStorage.GetEmbeddedResource("TypeGen.Core.Templates.Index.tpl");
             _indexExportTemplate = _internalStorage.GetEmbeddedResource("TypeGen.Core.Templates.IndexExport.tpl");
             _headingTemplate = _internalStorage.GetEmbeddedResource("TypeGen.Core.Templates.Heading.tpl");
+            _singleLineCommentTemplate = _internalStorage.GetEmbeddedResource("TypeGen.Core.Templates.SingleLineComment.tpl");
+            _lineBreakTemplate = _internalStorage.GetEmbeddedResource("TypeGen.Core.Templates.LineBreak.tpl");
         }
 
         public string FillClassTemplate(string imports, string name, string extends, string implements, string properties,
@@ -111,6 +117,20 @@ public string FillClassPropertyTemplate(string modifiers, string name, string ty
                 .Replace(GetTag("defaultValue"), defaultValue);
         }
 
+        public string FillClassPropertyTemplate(string name, string type, string defaultValue = null)
+        {
+            type = $": {type}";
+
+            defaultValue = string.IsNullOrWhiteSpace(defaultValue) ? "" : $" = {defaultValue}";
+
+            return ReplaceSpecialChars(_classPropertyTemplate)
+                .Replace(GetTag("modifiers"), "")
+                .Replace(GetTag("name"), name)
+                .Replace(GetTag("type"), type)
+                .Replace(GetTag("tsDoc"), "")
+                .Replace(GetTag("defaultValue"), defaultValue);
+        }
+
         public string FillInterfaceTemplate(string imports, string name, string extends, string properties, string tsDoc,
             string customHead,string customBody, string fileHeading = null)
         {
@@ -242,6 +262,14 @@ public string FillIndexExportTemplate(string filename)
 
         public string GetImplementsText(IEnumerable<string> names) => $" implements {string.Join(", ", names)}";
 
+        public string FillWithSingleLineComment(string comment)
+        {
+            return 
+                ReplaceSpecialChars(_lineBreakTemplate) + 
+                ReplaceSpecialChars(_singleLineCommentTemplate)
+                .Replace(GetTag("comment"), comment);
+        }
+
         private static string GetTag(string tagName) => $"$tg{{{tagName}}}";
 
         private string ReplaceSpecialChars(string template)
diff --git a/src/TypeGen/TypeGen.Core/SpecGeneration/Builders/ClassSpecBuilderBase.cs b/src/TypeGen/TypeGen.Core/SpecGeneration/Builders/ClassSpecBuilderBase.cs
index 15d9866d..d02a51fb 100644
--- a/src/TypeGen/TypeGen.Core/SpecGeneration/Builders/ClassSpecBuilderBase.cs
+++ b/src/TypeGen/TypeGen.Core/SpecGeneration/Builders/ClassSpecBuilderBase.cs
@@ -4,6 +4,7 @@
 
 namespace TypeGen.Core.SpecGeneration.Builders
 {
+    /// <inheritdoc />
     public abstract class ClassSpecBuilderBase<TSelf> : SpecBuilderBase,
         ICustomBaseTrait<TSelf>,
         ICustomHeaderTrait<TSelf>,
@@ -24,7 +25,8 @@ public abstract class ClassSpecBuilderBase<TSelf> : SpecBuilderBase,
         IStaticTrait<TSelf>,
         ITypeTrait<TSelf>,
         ITypeUnionsTrait<TSelf>,
-        IUndefinedTrait<TSelf>
+        IUndefinedTrait<TSelf>,
+        IAdditionalPropertiesTrait<TSelf>
         where TSelf : SpecBuilderBase
     {
         private readonly CustomBaseTrait<TSelf> _customBaseTrait;
@@ -47,7 +49,8 @@ public abstract class ClassSpecBuilderBase<TSelf> : SpecBuilderBase,
         private readonly TypeTrait<TSelf> _typeTrait;
         private readonly TypeUnionsTrait<TSelf> _typeUnionsTrait;
         private readonly UndefinedTrait<TSelf> _undefinedTrait;
-        
+        private readonly AdditionalPropertiesTrait<TSelf> _additionalPropertiesTrait;
+
         internal ClassSpecBuilderBase(TypeSpec typeSpec) : base(typeSpec)
         {
             MemberTrait = new MemberTrait<TSelf>(this as TSelf, typeSpec);
@@ -70,13 +73,14 @@ internal ClassSpecBuilderBase(TypeSpec typeSpec) : base(typeSpec)
             _typeTrait = new TypeTrait<TSelf>(this as TSelf, typeSpec, MemberTrait);
             _typeUnionsTrait = new TypeUnionsTrait<TSelf>(this as TSelf, typeSpec, MemberTrait);
             _undefinedTrait = new UndefinedTrait<TSelf>(this as TSelf, typeSpec, MemberTrait);
+            _additionalPropertiesTrait = new AdditionalPropertiesTrait<TSelf>(this as TSelf, typeSpec);
         }
 
         /// <inheritdoc />
         public TSelf CustomBase(string @base = null, string importPath = null, string originalTypeName = null, bool isDefaultExport = false,
             IEnumerable<ImplementedInterface> implementedInterfaces = null)
             => _customBaseTrait.CustomBase(@base, importPath, originalTypeName, isDefaultExport, implementedInterfaces);
-        
+
         /// <inheritdoc />
         public TSelf CustomBase(string @base = null, string importPath = null, string originalTypeName = null, bool isDefaultExport = false,
             params ImplementedInterface[] implementedInterfaces)
@@ -92,43 +96,43 @@ public TSelf CustomHeader(string header)
 
         /// <inheritdoc />
         public TSelf DefaultExport(bool enabled = true) => _defaultExportTrait.DefaultExport(enabled);
-        
+
         /// <inheritdoc />
         public TSelf DefaultTypeOutput(string outputDir) => _defaultTypeOutputTrait.DefaultTypeOutput(outputDir);
-        
+
         /// <inheritdoc />
         public TSelf DefaultValue(string defaultValue) => _defaultValueTrait.DefaultValue(defaultValue);
-        
+
         /// <inheritdoc />
         public TSelf IgnoreBase() => _ignoreBaseTrait.IgnoreBase();
-        
+
         /// <inheritdoc />
         public TSelf Ignore() => _ignoreTrait.Ignore();
-        
+
         /// <inheritdoc />
         public TSelf MemberName(string name) => _memberNameTrait.MemberName(name);
-        
+
         /// <inheritdoc />
         public TSelf Member(string memberName) => MemberTrait.Member(memberName);
 
         /// <inheritdoc />
         public TSelf NotNull() => _notNullTrait.NotNull();
-        
+
         /// <inheritdoc />
         public TSelf NotReadonly() => _notReadonlyTrait.NotReadonly();
-        
+
         /// <inheritdoc />
         public TSelf NotStatic() => _notStaticTrait.NotStatic();
 
         /// <inheritdoc />
         public TSelf NotUndefined() => _notUndefinedTrait.NotUndefined();
-        
+
         /// <inheritdoc />
         public TSelf Null() => _nullTrait.Null();
-        
+
         /// <inheritdoc />
         public TSelf Readonly() => _readonlyTrait.Readonly();
-        
+
         /// <inheritdoc />
         public TSelf Static() => _staticTrait.Static();
 
@@ -138,7 +142,7 @@ public TSelf Type(string typeName, string importPath = null, string originalType
 
         /// <inheritdoc />
         public TSelf Type(TsType tsType) => _typeTrait.Type(tsType);
-        
+
         /// <inheritdoc />
         public TSelf TypeUnions(IEnumerable<string> typeUnions) => _typeUnionsTrait.TypeUnions(typeUnions);
 
@@ -147,5 +151,18 @@ public TSelf Type(string typeName, string importPath = null, string originalType
 
         /// <inheritdoc />
         public TSelf Undefined() => _undefinedTrait.Undefined();
+
+        /// <summary>
+        /// Adds an additional property to the TypeScript class being generated.
+        /// The 'name' parameter can include access modifiers and the 'readonly' keyword,
+        /// allowing for flexible property definitions. For instance, you can define the
+        /// property as 'public name', 'private name', 'readonly name', etc.
+        /// </summary>
+        /// <param name="name">The name of the property, which can include access modifiers and keywords.</param>
+        /// <param name="type">The TypeScript type of the property.</param>
+        /// <param name="defaultValue">An optional default value for the property. If provided, it initializes the property with this value.</param>
+        /// <returns>The instance of the spec builder for method chaining.</returns>
+        public TSelf WithAdditionalProperty(string name, string type, string defaultValue = null) =>
+           _additionalPropertiesTrait.WithAdditionalProperty(name, type, defaultValue);
     }
 }
\ No newline at end of file
diff --git a/src/TypeGen/TypeGen.Core/SpecGeneration/Builders/Traits/AdditionalClassProperty.cs b/src/TypeGen/TypeGen.Core/SpecGeneration/Builders/Traits/AdditionalClassProperty.cs
new file mode 100644
index 00000000..ceddb4a3
--- /dev/null
+++ b/src/TypeGen/TypeGen.Core/SpecGeneration/Builders/Traits/AdditionalClassProperty.cs
@@ -0,0 +1,8 @@
+namespace TypeGen.Core.SpecGeneration.Builders.Traits;
+
+public class AdditionalClassProperty
+{
+    public string Name { get; set; }
+    public string Type { get; set; }
+    public string? DefaultValue { get; set; }
+}
diff --git a/src/TypeGen/TypeGen.Core/SpecGeneration/Builders/Traits/AdditionalPropertiesTrait.cs b/src/TypeGen/TypeGen.Core/SpecGeneration/Builders/Traits/AdditionalPropertiesTrait.cs
new file mode 100644
index 00000000..b78906a1
--- /dev/null
+++ b/src/TypeGen/TypeGen.Core/SpecGeneration/Builders/Traits/AdditionalPropertiesTrait.cs
@@ -0,0 +1,19 @@
+namespace TypeGen.Core.SpecGeneration.Builders.Traits;
+
+internal class AdditionalPropertiesTrait<TSpecBuilder> : IAdditionalPropertiesTrait<TSpecBuilder>
+{
+    private readonly TSpecBuilder _this;
+    private readonly TypeSpec _typeSpec;
+
+    public AdditionalPropertiesTrait(TSpecBuilder @this, TypeSpec typeSpec)
+    {
+        _this = @this;
+        _typeSpec = typeSpec;
+    }
+
+    public TSpecBuilder WithAdditionalProperty(string name, string type, string? defaultValue = null)
+    {
+        _typeSpec.AddAdditionalClassProperty(name, type, defaultValue);
+        return _this;
+    }
+}
\ No newline at end of file
diff --git a/src/TypeGen/TypeGen.Core/SpecGeneration/Builders/Traits/IAdditionalPropertiesTrait.cs b/src/TypeGen/TypeGen.Core/SpecGeneration/Builders/Traits/IAdditionalPropertiesTrait.cs
new file mode 100644
index 00000000..b4c29ded
--- /dev/null
+++ b/src/TypeGen/TypeGen.Core/SpecGeneration/Builders/Traits/IAdditionalPropertiesTrait.cs
@@ -0,0 +1,13 @@
+namespace TypeGen.Core.SpecGeneration.Builders.Traits;
+
+internal interface IAdditionalPropertiesTrait<TSpecBuilder>
+{
+    /// <summary>
+    /// Adds an additional property to the TypeScript class.
+    /// </summary>
+    /// <param name="name">The name of the property.</param>
+    /// <param name="type">The TypeScript type of the property.</param>
+    /// <param name="defaultValue">The TypeScript default value of the property.</param>
+    /// <returns>The current instance of <see cref="TSpecBuilder"/>.</returns>
+    TSpecBuilder WithAdditionalProperty(string name, string type, string? defaultValue = null);
+}
diff --git a/src/TypeGen/TypeGen.Core/SpecGeneration/TypeSpec.cs b/src/TypeGen/TypeGen.Core/SpecGeneration/TypeSpec.cs
index 89d131c6..692f611b 100644
--- a/src/TypeGen/TypeGen.Core/SpecGeneration/TypeSpec.cs
+++ b/src/TypeGen/TypeGen.Core/SpecGeneration/TypeSpec.cs
@@ -1,57 +1,72 @@
 using System;
 using System.Collections.Generic;
+using TypeGen.Core.SpecGeneration.Builders.Traits;
 using TypeGen.Core.TypeAnnotations;
 
-namespace TypeGen.Core.SpecGeneration
+namespace TypeGen.Core.SpecGeneration;
+
+internal class TypeSpec
 {
-    internal class TypeSpec
+    private readonly List<Attribute> _additionalAttributes;
+    private readonly Dictionary<string, IList<Attribute>> _memberAttributes;
+    private readonly List<AdditionalClassProperty> _additionalClassProperties = new List<AdditionalClassProperty>();
+
+    public ExportAttribute ExportAttribute { get; }
+
+    public IList<Attribute> AdditionalAttributes => _additionalAttributes;
+
+    public IDictionary<string, IList<Attribute>> MemberAttributes => _memberAttributes;
+
+    public IEnumerable<AdditionalClassProperty> AdditionalClassProperties => _additionalClassProperties;
+
+    public TypeSpec(ExportAttribute exportAttribute)
     {
-        private readonly List<Attribute> _additionalAttributes;
-        private readonly Dictionary<string, IList<Attribute>> _memberAttributes;
+        ExportAttribute = exportAttribute;
+        _memberAttributes = new Dictionary<string, IList<Attribute>>();
+        _additionalAttributes = new List<Attribute>();
+    }
 
-        public ExportAttribute ExportAttribute { get; }
+    public void AddMember(string memberName) => _memberAttributes[memberName] = new List<Attribute>();
 
-        public IList<Attribute> AdditionalAttributes => _additionalAttributes;
+    public void AddCustomBaseAttribute(string @base = null, string importPath = null, string originalTypeName = null, bool isDefaultExport = false,
+        params object[] implementedInterfaces)
+        => AddAdditionalAttribute(new TsCustomBaseAttribute(@base, importPath, originalTypeName, isDefaultExport, implementedInterfaces));
+    public void AddDefaultExportAttribute(bool enabled = true) => AddAdditionalAttribute(new TsDefaultExportAttribute(enabled));
+    public void AddDefaultTypeOutputAttribute(string memberName, string outputDir) => AddMemberAttribute(memberName, new TsDefaultTypeOutputAttribute(outputDir));
+    public void AddDefaultValueAttribute(string memberName, string defaultValue) => AddMemberAttribute(memberName, new TsDefaultValueAttribute(defaultValue));
+    public void AddIgnoreAttribute(string memberName) => AddMemberAttribute(memberName, new TsIgnoreAttribute());
+    public void AddIgnoreBaseAttribute() => AddAdditionalAttribute(new TsIgnoreBaseAttribute());
+    public void SetCustomHeader(string header) { ExportAttribute.CustomHeader = header; }
+    public void SetCustomBody(string body) { ExportAttribute.CustomBody = body; }
+    public void AddMemberNameAttribute(string memberName, string name) => AddMemberAttribute(memberName, new TsMemberNameAttribute(name));
+    public void AddNotNullAttribute(string memberName) => AddMemberAttribute(memberName, new TsNotNullAttribute());
+    public void AddNotReadonlyAttribute(string memberName) => AddMemberAttribute(memberName, new TsNotReadonlyAttribute());
+    public void AddNotStaticAttribute(string memberName) => AddMemberAttribute(memberName, new TsNotStaticAttribute());
+    public void AddNotUndefinedAttribute(string memberName) => AddMemberAttribute(memberName, new TsNotUndefinedAttribute());
+    public void AddNullAttribute(string memberName) => AddMemberAttribute(memberName, new TsNullAttribute());
+    public void AddOptionalAttribute(string memberName) => AddMemberAttribute(memberName, new TsOptionalAttribute());
+    public void AddReadonlyAttribute(string memberName) => AddMemberAttribute(memberName, new TsReadonlyAttribute());
+    public void AddStaticAttribute(string memberName) => AddMemberAttribute(memberName, new TsStaticAttribute());
+    public void AddStringInitializersAttribute(bool enabled = true) => AddAdditionalAttribute(new TsStringInitializersAttribute(enabled));
+    public void AddTypeAttribute(string memberName, TsType tsType) => AddMemberAttribute(memberName, new TsTypeAttribute(tsType));
+    public void AddTypeAttribute(string memberName, string typeName, string importPath = null, string originalTypeName = null, bool isDefaultExport = false)
+        => AddMemberAttribute(memberName, new TsTypeAttribute(typeName, importPath, originalTypeName, isDefaultExport));
+    public void AddTypeUnionsAttribute(string memberName, IEnumerable<string> typeUnions) => AddMemberAttribute(memberName, new TsTypeUnionsAttribute(typeUnions));
+    public void AddTypeUnionsAttribute(string memberName, params string[] typeUnions) => AddMemberAttribute(memberName, new TsTypeUnionsAttribute(typeUnions));
+    public void AddUndefinedAttribute(string memberName) => AddMemberAttribute(memberName, new TsUndefinedAttribute());
 
-        public IDictionary<string, IList<Attribute>> MemberAttributes => _memberAttributes;
+    private void AddMemberAttribute(string memberName, Attribute attribute) => MemberAttributes[memberName].Add(attribute);
+    private void AddAdditionalAttribute(Attribute attribute) => _additionalAttributes.Add(attribute);
 
-        public TypeSpec(ExportAttribute exportAttribute)
+    public void AddAdditionalClassProperty(string name, string type, string? defaultValue)
+    {
+        _additionalClassProperties.Add(new AdditionalClassProperty
         {
-            ExportAttribute = exportAttribute;
-            _memberAttributes = new Dictionary<string, IList<Attribute>>();
-            _additionalAttributes = new List<Attribute>();
-        }
-
-        public void AddMember(string memberName) => _memberAttributes[memberName] = new List<Attribute>();
-
-        public void AddCustomBaseAttribute(string @base = null, string importPath = null, string originalTypeName = null, bool isDefaultExport = false,
-            params object[] implementedInterfaces)
-            => AddAdditionalAttribute(new TsCustomBaseAttribute(@base, importPath, originalTypeName, isDefaultExport, implementedInterfaces));
-        public void AddDefaultExportAttribute(bool enabled = true) => AddAdditionalAttribute(new TsDefaultExportAttribute(enabled));
-        public void AddDefaultTypeOutputAttribute(string memberName, string outputDir) => AddMemberAttribute(memberName, new TsDefaultTypeOutputAttribute(outputDir));
-        public void AddDefaultValueAttribute(string memberName, string defaultValue) => AddMemberAttribute(memberName, new TsDefaultValueAttribute(defaultValue));
-        public void AddIgnoreAttribute(string memberName) => AddMemberAttribute(memberName, new TsIgnoreAttribute());
-        public void AddIgnoreBaseAttribute() => AddAdditionalAttribute(new TsIgnoreBaseAttribute());
-        public void SetCustomHeader(string header) { ExportAttribute.CustomHeader = header; }
-        public void SetCustomBody(string body) { ExportAttribute.CustomBody = body; }
-        public void AddMemberNameAttribute(string memberName, string name) => AddMemberAttribute(memberName, new TsMemberNameAttribute(name));
-        public void AddNotNullAttribute(string memberName) => AddMemberAttribute(memberName, new TsNotNullAttribute());
-        public void AddNotReadonlyAttribute(string memberName) => AddMemberAttribute(memberName, new TsNotReadonlyAttribute());
-        public void AddNotStaticAttribute(string memberName) => AddMemberAttribute(memberName, new TsNotStaticAttribute());
-        public void AddNotUndefinedAttribute(string memberName) => AddMemberAttribute(memberName, new TsNotUndefinedAttribute());
-        public void AddNullAttribute(string memberName) => AddMemberAttribute(memberName, new TsNullAttribute());
-        public void AddOptionalAttribute(string memberName) => AddMemberAttribute(memberName, new TsOptionalAttribute());
-        public void AddReadonlyAttribute(string memberName) => AddMemberAttribute(memberName, new TsReadonlyAttribute());
-        public void AddStaticAttribute(string memberName) => AddMemberAttribute(memberName, new TsStaticAttribute());
-        public void AddStringInitializersAttribute(bool enabled = true) => AddAdditionalAttribute(new TsStringInitializersAttribute(enabled));
-        public void AddTypeAttribute(string memberName, TsType tsType) => AddMemberAttribute(memberName, new TsTypeAttribute(tsType));
-        public void AddTypeAttribute(string memberName, string typeName, string importPath = null, string originalTypeName = null, bool isDefaultExport = false)
-            => AddMemberAttribute(memberName, new TsTypeAttribute(typeName, importPath, originalTypeName, isDefaultExport));
-        public void AddTypeUnionsAttribute(string memberName, IEnumerable<string> typeUnions) => AddMemberAttribute(memberName, new TsTypeUnionsAttribute(typeUnions));
-        public void AddTypeUnionsAttribute(string memberName, params string[] typeUnions) => AddMemberAttribute(memberName, new TsTypeUnionsAttribute(typeUnions));
-        public void AddUndefinedAttribute(string memberName) => AddMemberAttribute(memberName, new TsUndefinedAttribute());
-
-        private void AddMemberAttribute(string memberName, Attribute attribute) => MemberAttributes[memberName].Add(attribute);
-        private void AddAdditionalAttribute(Attribute attribute) => _additionalAttributes.Add(attribute);
+            Name = name,
+            Type = type,
+            DefaultValue = defaultValue,
+        });
     }
+
+
 }
diff --git a/src/TypeGen/TypeGen.Core/Templates/LineBreak.tpl b/src/TypeGen/TypeGen.Core/Templates/LineBreak.tpl
new file mode 100644
index 00000000..8b137891
--- /dev/null
+++ b/src/TypeGen/TypeGen.Core/Templates/LineBreak.tpl
@@ -0,0 +1 @@
+
diff --git a/src/TypeGen/TypeGen.Core/Templates/SingleLineComment.tpl b/src/TypeGen/TypeGen.Core/Templates/SingleLineComment.tpl
new file mode 100644
index 00000000..76b6214a
--- /dev/null
+++ b/src/TypeGen/TypeGen.Core/Templates/SingleLineComment.tpl
@@ -0,0 +1 @@
+$tg{tab}// $tg{comment}
diff --git a/src/TypeGen/TypeGen.Core/TypeGen.Core.csproj b/src/TypeGen/TypeGen.Core/TypeGen.Core.csproj
index ea861bd7..cc79f81c 100644
--- a/src/TypeGen/TypeGen.Core/TypeGen.Core.csproj
+++ b/src/TypeGen/TypeGen.Core/TypeGen.Core.csproj
@@ -3,8 +3,7 @@
     <TargetFrameworks>netstandard2.0;net8.0</TargetFrameworks>
     <DocumentationFile>TypeGen.Core.xml</DocumentationFile>
     <LangVersion>latest</LangVersion>
-    <AssemblyVersion>5.0.0.0</AssemblyVersion>
-    <FileVersion>5.0.0.0</FileVersion>
+    <AssemblyVersion>5.0.0.1</AssemblyVersion>
   </PropertyGroup>
   <ItemGroup>
     <None Remove="Templates\Class.tpl" />
@@ -21,11 +20,15 @@
     <None Remove="Templates\InterfaceProperty.tpl" />
     <None Remove="Templates\Index.tpl" />
     <None Remove="Templates\IndexExport.tpl" />
+    <None Remove="Templates\LineBreak.tpl" />
+    <None Remove="Templates\SingleLineComment.tpl" />
   </ItemGroup>
   <ItemGroup>
     <EmbeddedResource Include="Templates\Class.tpl" />
     <EmbeddedResource Include="Templates\ClassDefaultExport.tpl" />
     <EmbeddedResource Include="Templates\ClassProperty.tpl" />
+    <EmbeddedResource Include="Templates\LineBreak.tpl" />
+    <EmbeddedResource Include="Templates\SingleLineComment.tpl" />
     <EmbeddedResource Include="Templates\EnumUnionTypeDefaultExport.tpl" />
     <EmbeddedResource Include="Templates\EnumUnionType.tpl" />
     <EmbeddedResource Include="Templates\Enum.tpl" />
diff --git a/src/TypeGen/TypeGen.FileContentTest/AdditionalProperties/AdditionalClassPropertiesTest.cs b/src/TypeGen/TypeGen.FileContentTest/AdditionalProperties/AdditionalClassPropertiesTest.cs
new file mode 100644
index 00000000..3a43f8b3
--- /dev/null
+++ b/src/TypeGen/TypeGen.FileContentTest/AdditionalProperties/AdditionalClassPropertiesTest.cs
@@ -0,0 +1,38 @@
+using System.Threading.Tasks;
+using TypeGen.Core.Generator;
+using TypeGen.Core.SpecGeneration;
+using TypeGen.FileContentTest.AdditionalClassProperties.Entities;
+using TypeGen.FileContentTest.TestingUtils;
+using Xunit;
+
+namespace TypeGen.FileContentTest.AdditionalClassProperties
+{
+    public class AdditionalClassPropertiesTest : GenerationTestBase
+    {
+        [Fact]
+        public async Task ClassWithAdditionalClassProperties_Test()
+        {
+            var type = typeof(ClassWithAdditionalClassProperties);
+            const string expectedLocation = "TypeGen.FileContentTest.AdditionalProperties.Expected.class-with-additional-class-properties.ts";
+            var generationSpec = new ClassWithAdditionalPropertiesGenerationSpec();
+            var generatorOptions = new GeneratorOptions { };
+            
+            await TestGenerationSpec(type, expectedLocation, generationSpec, generatorOptions);
+        }
+        
+        private class ClassWithAdditionalPropertiesGenerationSpec : GenerationSpec
+        {
+            public ClassWithAdditionalPropertiesGenerationSpec()
+            {
+                AddClass<ClassWithAdditionalClassProperties>()
+                    .WithAdditionalProperty("public email", "string")
+                    .WithAdditionalProperty("greetingMessage", "string", "'Hello, World!'")
+                    .WithAdditionalProperty("emptyString", "string", "''")
+                    .WithAdditionalProperty("creationDate", "Date")
+                    .WithAdditionalProperty("username", "string")
+                    .WithAdditionalProperty("age", "number")
+                    .WithAdditionalProperty("status", "'active' | 'inactive' | 'pending'");
+            }
+        }
+    }
+}
diff --git a/src/TypeGen/TypeGen.FileContentTest/AdditionalProperties/Entities/ClassWithAdditionalClassProperties.cs b/src/TypeGen/TypeGen.FileContentTest/AdditionalProperties/Entities/ClassWithAdditionalClassProperties.cs
new file mode 100644
index 00000000..f548d754
--- /dev/null
+++ b/src/TypeGen/TypeGen.FileContentTest/AdditionalProperties/Entities/ClassWithAdditionalClassProperties.cs
@@ -0,0 +1,8 @@
+using System;
+
+namespace TypeGen.FileContentTest.AdditionalClassProperties.Entities;
+
+public class ClassWithAdditionalClassProperties
+{
+    public string name;
+}
\ No newline at end of file
diff --git a/src/TypeGen/TypeGen.FileContentTest/AdditionalProperties/Expected/class-with-additional-class-properties.ts b/src/TypeGen/TypeGen.FileContentTest/AdditionalProperties/Expected/class-with-additional-class-properties.ts
new file mode 100644
index 00000000..7909b555
--- /dev/null
+++ b/src/TypeGen/TypeGen.FileContentTest/AdditionalProperties/Expected/class-with-additional-class-properties.ts
@@ -0,0 +1,17 @@
+/**
+ * This is a TypeGen auto-generated file.
+ * Any changes made to this file can be lost when this file is regenerated.
+ */
+
+export class ClassWithAdditionalClassProperties {
+    name: string;
+
+    // Additional properties
+    public email: string;
+    greetingMessage: string = 'Hello, World!';
+    emptyString: string = '';
+    creationDate: Date;
+    username: string;
+    age: number;
+    status: 'active' | 'inactive' | 'pending';
+}
diff --git a/src/TypeGen/TypeGen.FileContentTest/TypeGen.FileContentTest.csproj b/src/TypeGen/TypeGen.FileContentTest/TypeGen.FileContentTest.csproj
index 1e4409ea..dba7ec9b 100644
--- a/src/TypeGen/TypeGen.FileContentTest/TypeGen.FileContentTest.csproj
+++ b/src/TypeGen/TypeGen.FileContentTest/TypeGen.FileContentTest.csproj
@@ -17,6 +17,7 @@
 	</PropertyGroup>
 
 	<ItemGroup>
+	  <None Remove="AdditionalProperties\Expected\class-with-additional-class-properties.ts" />
 	  <None Remove="Generator\Expected\constants-only.ts" />
 	</ItemGroup>
 
@@ -32,6 +33,7 @@
 	</ItemGroup>
 
 	<ItemGroup>
+		<EmbeddedResource Include="AdditionalProperties\Expected\class-with-additional-class-properties.ts" />
 		<EmbeddedResource Include="Blacklist\Expected\class-with-blacklisted-base.ts" />
 		<EmbeddedResource Include="Blacklist\Expected\class-with-blacklisted-interface.ts" />
 		<EmbeddedResource Include="Blacklist\Expected\interface-with-blacklisted-base.ts" />