diff --git a/.vscode/extensions.json b/.vscode/extensions.json
index ec8565fa..7d3949f2 100644
--- a/.vscode/extensions.json
+++ b/.vscode/extensions.json
@@ -1,6 +1,5 @@
 {
     "recommendations": [
-        "formulahendry.dotnet-test-explorer",
         "ms-dotnettools.csharp",
         "editorconfig.editorconfig"
     ]
diff --git a/src/Microsoft.OpenApi.OData.Reader/Generator/OpenApiErrorSchemaGenerator.cs b/src/Microsoft.OpenApi.OData.Reader/Generator/OpenApiErrorSchemaGenerator.cs
index 879a2665..a5fa11c1 100644
--- a/src/Microsoft.OpenApi.OData.Reader/Generator/OpenApiErrorSchemaGenerator.cs
+++ b/src/Microsoft.OpenApi.OData.Reader/Generator/OpenApiErrorSchemaGenerator.cs
@@ -6,9 +6,11 @@
 using System.Collections.Generic;
 using System.Linq;
 using Microsoft.OData.Edm;
+using Microsoft.OpenApi.Interfaces;
 using Microsoft.OpenApi.Models;
 using Microsoft.OpenApi.OData.Common;
 using Microsoft.OpenApi.OData.Edm;
+using Microsoft.OpenApi.OData.OpenApiExtensions;
 
 namespace Microsoft.OpenApi.OData.Generator
 {
@@ -133,7 +135,8 @@ public static OpenApiSchema CreateErrorMainSchema(string rootNamespaceName)
                         "code", new OpenApiSchema { Type = "string", Nullable = false }
                     },
                     {
-                        "message", new OpenApiSchema { Type = "string", Nullable = false, }
+                        "message", new OpenApiSchema { Type = "string", Nullable = false, Extensions = new Dictionary<string, IOpenApiExtension> 
+                                                                                    { { OpenApiPrimaryErrorMessageExtension.Name, new OpenApiPrimaryErrorMessageExtension { IsPrimaryErrorMessage = true } } } }
                     },
                     {
                         "target", new OpenApiSchema { Type = "string", Nullable = true }
diff --git a/src/Microsoft.OpenApi.OData.Reader/Microsoft.OpenAPI.OData.Reader.csproj b/src/Microsoft.OpenApi.OData.Reader/Microsoft.OpenAPI.OData.Reader.csproj
index a5a2aed7..4d2a870e 100644
--- a/src/Microsoft.OpenApi.OData.Reader/Microsoft.OpenAPI.OData.Reader.csproj
+++ b/src/Microsoft.OpenApi.OData.Reader/Microsoft.OpenAPI.OData.Reader.csproj
@@ -15,7 +15,7 @@
     <TargetFrameworks>netstandard2.0</TargetFrameworks>
     <PackageId>Microsoft.OpenApi.OData</PackageId>
     <SignAssembly>true</SignAssembly>
-    <Version>1.5.0-preview3</Version>
+    <Version>1.5.0-preview4</Version>
     <Description>This package contains the codes you need to convert OData CSDL to Open API Document of Model.</Description>
     <Copyright>© Microsoft Corporation. All rights reserved.</Copyright>
     <PackageTags>Microsoft OpenApi OData EDM</PackageTags>
diff --git a/src/Microsoft.OpenApi.OData.Reader/OpenApiExtensions/OpenApiPrimaryErrorMessageExtension.cs b/src/Microsoft.OpenApi.OData.Reader/OpenApiExtensions/OpenApiPrimaryErrorMessageExtension.cs
new file mode 100644
index 00000000..4aa4ed6e
--- /dev/null
+++ b/src/Microsoft.OpenApi.OData.Reader/OpenApiExtensions/OpenApiPrimaryErrorMessageExtension.cs
@@ -0,0 +1,45 @@
+// ------------------------------------------------------------
+//  Copyright (c) Microsoft Corporation.  All rights reserved.
+//  Licensed under the MIT License (MIT). See LICENSE in the repo root for license information.
+// ------------------------------------------------------------
+
+using System;
+using Microsoft.OpenApi.Any;
+using Microsoft.OpenApi.Interfaces;
+using Microsoft.OpenApi.Writers;
+
+namespace Microsoft.OpenApi.OData.OpenApiExtensions;
+
+/// <summary>
+/// Extension element for OpenAPI to add tag the primary error message to use on error types. x-ms-primary-error-message
+/// </summary>
+public class OpenApiPrimaryErrorMessageExtension : IOpenApiExtension
+{
+	/// <summary>
+	/// Name of the extension as used in the description.
+	/// </summary>
+	public static string Name => "x-ms-primary-error-message";
+	/// <inheritdoc />
+    public void Write(IOpenApiWriter writer, OpenApiSpecVersion specVersion)
+    {
+        if(writer == null)
+            throw new ArgumentNullException(nameof(writer));
+		writer.WriteValue(IsPrimaryErrorMessage);
+    }
+	/// <summary>
+	/// Whether this property is the primary error message to use on error types.
+	/// </summary>
+	public bool IsPrimaryErrorMessage { get; set; }
+	/// <summary>
+    /// Parses the <see cref="IOpenApiAny"/> to <see cref="OpenApiPrimaryErrorMessageExtension"/>.
+    /// </summary>
+    /// <param name="source">The source object.</param>
+    /// <returns>The <see cref="OpenApiPrimaryErrorMessageExtension"/>.</returns>
+	public static OpenApiPrimaryErrorMessageExtension Parse(IOpenApiAny source)
+	{
+		if (source is not OpenApiBoolean rawObject) throw new ArgumentOutOfRangeException(nameof(source));
+		return new OpenApiPrimaryErrorMessageExtension() {
+			IsPrimaryErrorMessage = rawObject.Value
+		};
+	}
+}
\ No newline at end of file
diff --git a/src/Microsoft.OpenApi.OData.Reader/PublicAPI.Unshipped.txt b/src/Microsoft.OpenApi.OData.Reader/PublicAPI.Unshipped.txt
index b4684880..2059591e 100644
--- a/src/Microsoft.OpenApi.OData.Reader/PublicAPI.Unshipped.txt
+++ b/src/Microsoft.OpenApi.OData.Reader/PublicAPI.Unshipped.txt
@@ -58,6 +58,13 @@ Microsoft.OpenApi.OData.OpenApiExtensions.OpenApiEnumFlagsExtension.OpenApiEnumF
 Microsoft.OpenApi.OData.OpenApiExtensions.OpenApiEnumFlagsExtension.Style.get -> string
 Microsoft.OpenApi.OData.OpenApiExtensions.OpenApiEnumFlagsExtension.Style.set -> void
 Microsoft.OpenApi.OData.OpenApiExtensions.OpenApiEnumFlagsExtension.Write(Microsoft.OpenApi.Writers.IOpenApiWriter writer, Microsoft.OpenApi.OpenApiSpecVersion specVersion) -> void
+Microsoft.OpenApi.OData.OpenApiExtensions.OpenApiPrimaryErrorMessageExtension
+Microsoft.OpenApi.OData.OpenApiExtensions.OpenApiPrimaryErrorMessageExtension.OpenApiPrimaryErrorMessageExtension() -> void
+Microsoft.OpenApi.OData.OpenApiExtensions.OpenApiPrimaryErrorMessageExtension.Write(Microsoft.OpenApi.Writers.IOpenApiWriter writer, Microsoft.OpenApi.OpenApiSpecVersion specVersion) -> void
+static Microsoft.OpenApi.OData.OpenApiExtensions.OpenApiPrimaryErrorMessageExtension.Name.get -> string
+Microsoft.OpenApi.OData.OpenApiExtensions.OpenApiPrimaryErrorMessageExtension.IsPrimaryErrorMessage.get -> bool
+Microsoft.OpenApi.OData.OpenApiExtensions.OpenApiPrimaryErrorMessageExtension.IsPrimaryErrorMessage.set -> void
+static Microsoft.OpenApi.OData.OpenApiExtensions.OpenApiPrimaryErrorMessageExtension.Parse(Microsoft.OpenApi.Any.IOpenApiAny source) -> Microsoft.OpenApi.OData.OpenApiExtensions.OpenApiPrimaryErrorMessageExtension
 Microsoft.OpenApi.OData.Vocabulary.Core.LinkRelKey
 Microsoft.OpenApi.OData.Vocabulary.Core.LinkRelKey.Action = 6 -> Microsoft.OpenApi.OData.Vocabulary.Core.LinkRelKey
 Microsoft.OpenApi.OData.Vocabulary.Core.LinkRelKey.Create = 2 -> Microsoft.OpenApi.OData.Vocabulary.Core.LinkRelKey
diff --git a/test/Microsoft.OpenAPI.OData.Reader.Tests/OpenApiExtensions/OpenApiPrimaryErrorMessageExtensionTests.cs b/test/Microsoft.OpenAPI.OData.Reader.Tests/OpenApiExtensions/OpenApiPrimaryErrorMessageExtensionTests.cs
new file mode 100644
index 00000000..6b400671
--- /dev/null
+++ b/test/Microsoft.OpenAPI.OData.Reader.Tests/OpenApiExtensions/OpenApiPrimaryErrorMessageExtensionTests.cs
@@ -0,0 +1,56 @@
+// ------------------------------------------------------------
+//  Copyright (c) Microsoft Corporation.  All rights reserved.
+//  Licensed under the MIT License (MIT). See LICENSE in the repo root for license information.
+// ------------------------------------------------------------
+
+using System;
+using System.IO;
+using Microsoft.OpenApi.Any;
+using Microsoft.OpenApi.Writers;
+using Xunit;
+
+namespace Microsoft.OpenApi.OData.OpenApiExtensions.Tests;
+
+public class OpenApiPrimaryErrorMessageExtensionTests
+{
+	[Fact]
+	public void ExtensionNameMatchesExpected()
+	{
+		// Act
+		string name = OpenApiPrimaryErrorMessageExtension.Name;
+		string expectedName = "x-ms-primary-error-message";
+
+		// Assert
+		Assert.Equal(expectedName, name);
+	}
+	[Fact]
+	public void WritesValue()
+	{
+		// Arrange
+		OpenApiPrimaryErrorMessageExtension extension = new() {
+			IsPrimaryErrorMessage = true
+		};
+		using TextWriter sWriter = new StringWriter();
+		OpenApiJsonWriter writer = new(sWriter);
+
+		// Act
+		extension.Write(writer, OpenApiSpecVersion.OpenApi3_0);
+		string result = sWriter.ToString();
+
+		// Assert
+		Assert.True(extension.IsPrimaryErrorMessage);
+		Assert.Equal("true", result);
+	}
+	[Fact]
+	public void ParsesValue()
+	{
+		// Arrange
+		var value = new OpenApiBoolean(true);
+
+		// Act
+		var extension = OpenApiPrimaryErrorMessageExtension.Parse(value);
+
+		// Assert
+		Assert.True(extension.IsPrimaryErrorMessage);
+	}
+}
diff --git a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Basic.OpenApi.V2.json b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Basic.OpenApi.V2.json
index fc0be48c..5be9fd5a 100644
--- a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Basic.OpenApi.V2.json
+++ b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Basic.OpenApi.V2.json
@@ -1034,7 +1034,8 @@
           "type": "string"
         },
         "message": {
-          "type": "string"
+          "type": "string",
+          "x-ms-primary-error-message": true
         },
         "target": {
           "type": "string"
diff --git a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Basic.OpenApi.V2.yaml b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Basic.OpenApi.V2.yaml
index d7b71b02..efedb95e 100644
--- a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Basic.OpenApi.V2.yaml
+++ b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Basic.OpenApi.V2.yaml
@@ -679,6 +679,7 @@ definitions:
         type: string
       message:
         type: string
+        x-ms-primary-error-message: true
       target:
         type: string
       details:
diff --git a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Basic.OpenApi.json b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Basic.OpenApi.json
index 9af2ecaa..c2e137ea 100644
--- a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Basic.OpenApi.json
+++ b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Basic.OpenApi.json
@@ -1137,7 +1137,8 @@
             "type": "string"
           },
           "message": {
-            "type": "string"
+            "type": "string",
+            "x-ms-primary-error-message": true
           },
           "target": {
             "type": "string",
diff --git a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Basic.OpenApi.yaml b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Basic.OpenApi.yaml
index d9c07846..81208bcf 100644
--- a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Basic.OpenApi.yaml
+++ b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Basic.OpenApi.yaml
@@ -748,6 +748,7 @@ components:
           type: string
         message:
           type: string
+          x-ms-primary-error-message: true
         target:
           type: string
           nullable: true
diff --git a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Empty.OpenApi.V2.json b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Empty.OpenApi.V2.json
index 9048e01d..972656d0 100644
--- a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Empty.OpenApi.V2.json
+++ b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Empty.OpenApi.V2.json
@@ -33,7 +33,8 @@
           "type": "string"
         },
         "message": {
-          "type": "string"
+          "type": "string",
+          "x-ms-primary-error-message": true
         },
         "target": {
           "type": "string"
diff --git a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Empty.OpenApi.V2.yaml b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Empty.OpenApi.V2.yaml
index 6f24fc47..1f101507 100644
--- a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Empty.OpenApi.V2.yaml
+++ b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Empty.OpenApi.V2.yaml
@@ -25,6 +25,7 @@ definitions:
         type: string
       message:
         type: string
+        x-ms-primary-error-message: true
       target:
         type: string
       details:
diff --git a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Empty.OpenApi.json b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Empty.OpenApi.json
index 9d42e533..6ed11956 100644
--- a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Empty.OpenApi.json
+++ b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Empty.OpenApi.json
@@ -35,7 +35,8 @@
             "type": "string"
           },
           "message": {
-            "type": "string"
+            "type": "string",
+            "x-ms-primary-error-message": true
           },
           "target": {
             "type": "string",
diff --git a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Empty.OpenApi.yaml b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Empty.OpenApi.yaml
index cb39dcf2..9d790631 100644
--- a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Empty.OpenApi.yaml
+++ b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Empty.OpenApi.yaml
@@ -25,6 +25,7 @@ components:
           type: string
         message:
           type: string
+          x-ms-primary-error-message: true
         target:
           type: string
           nullable: true
diff --git a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Multiple.Schema.OpenApi.V2.json b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Multiple.Schema.OpenApi.V2.json
index 0a7e96a2..b636b2a2 100644
--- a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Multiple.Schema.OpenApi.V2.json
+++ b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Multiple.Schema.OpenApi.V2.json
@@ -5771,7 +5771,8 @@
           "type": "string"
         },
         "message": {
-          "type": "string"
+          "type": "string",
+          "x-ms-primary-error-message": true
         },
         "target": {
           "type": "string"
diff --git a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Multiple.Schema.OpenApi.V2.yaml b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Multiple.Schema.OpenApi.V2.yaml
index b3417eb3..c77bf1b6 100644
--- a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Multiple.Schema.OpenApi.V2.yaml
+++ b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Multiple.Schema.OpenApi.V2.yaml
@@ -4201,6 +4201,7 @@ definitions:
         type: string
       message:
         type: string
+        x-ms-primary-error-message: true
       target:
         type: string
       details:
diff --git a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Multiple.Schema.OpenApi.json b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Multiple.Schema.OpenApi.json
index fb014b15..1fb9df64 100644
--- a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Multiple.Schema.OpenApi.json
+++ b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Multiple.Schema.OpenApi.json
@@ -6505,7 +6505,8 @@
             "type": "string"
           },
           "message": {
-            "type": "string"
+            "type": "string",
+            "x-ms-primary-error-message": true
           },
           "target": {
             "type": "string",
diff --git a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Multiple.Schema.OpenApi.yaml b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Multiple.Schema.OpenApi.yaml
index 41391f52..bbae78d1 100644
--- a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Multiple.Schema.OpenApi.yaml
+++ b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/Multiple.Schema.OpenApi.yaml
@@ -4689,6 +4689,7 @@ components:
           type: string
         message:
           type: string
+          x-ms-primary-error-message: true
         target:
           type: string
           nullable: true
diff --git a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/TripService.OpenApi.V2.json b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/TripService.OpenApi.V2.json
index 63189d75..b48b8ec7 100644
--- a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/TripService.OpenApi.V2.json
+++ b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/TripService.OpenApi.V2.json
@@ -28144,7 +28144,8 @@
           "type": "string"
         },
         "message": {
-          "type": "string"
+          "type": "string",
+          "x-ms-primary-error-message": true
         },
         "target": {
           "type": "string"
diff --git a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/TripService.OpenApi.V2.yaml b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/TripService.OpenApi.V2.yaml
index 86df0ff5..f7e9a04f 100644
--- a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/TripService.OpenApi.V2.yaml
+++ b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/TripService.OpenApi.V2.yaml
@@ -19773,6 +19773,7 @@ definitions:
         type: string
       message:
         type: string
+        x-ms-primary-error-message: true
       target:
         type: string
       details:
diff --git a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/TripService.OpenApi.json b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/TripService.OpenApi.json
index 8f9b290f..d748228e 100644
--- a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/TripService.OpenApi.json
+++ b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/TripService.OpenApi.json
@@ -31534,7 +31534,8 @@
             "type": "string"
           },
           "message": {
-            "type": "string"
+            "type": "string",
+            "x-ms-primary-error-message": true
           },
           "target": {
             "type": "string",
diff --git a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/TripService.OpenApi.yaml b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/TripService.OpenApi.yaml
index 5f613dc2..5e7f3fbc 100644
--- a/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/TripService.OpenApi.yaml
+++ b/test/Microsoft.OpenAPI.OData.Reader.Tests/Resources/TripService.OpenApi.yaml
@@ -21959,6 +21959,7 @@ components:
           type: string
         message:
           type: string
+          x-ms-primary-error-message: true
         target:
           type: string
           nullable: true