diff --git a/src/Microsoft.OpenApi.OData.Reader/Edm/ODataOperationSegment.cs b/src/Microsoft.OpenApi.OData.Reader/Edm/ODataOperationSegment.cs
index edf8e32b..af2b66b4 100644
--- a/src/Microsoft.OpenApi.OData.Reader/Edm/ODataOperationSegment.cs
+++ b/src/Microsoft.OpenApi.OData.Reader/Edm/ODataOperationSegment.cs
@@ -5,6 +5,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Data.Common;
 using System.Linq;
 using System.Text;
 using Microsoft.OData.Edm;
@@ -145,7 +146,9 @@ private string FunctionName(IEdmFunction function, OpenApiConvertSettings settin
             {
                 string uniqueName = Utils.GetUniqueName(p.Name, parameters);
                 var quote = p.Type.Definition.ShouldPathParameterBeQuoted(settings) ? "'" : string.Empty;
-                return p.Name + $"={quote}{{{uniqueName}}}{quote}";
+                return p is IEdmOptionalParameter
+                    ? p.Name + $"={quote}@{uniqueName}{quote}"
+                    : p.Name + $"={quote}{{{uniqueName}}}{quote}";
             })));
 
             functionName.Append(")");
diff --git a/src/Microsoft.OpenApi.OData.Reader/Generator/OpenApiParameterGenerator.cs b/src/Microsoft.OpenApi.OData.Reader/Generator/OpenApiParameterGenerator.cs
index cbd2e01d..d273f435 100644
--- a/src/Microsoft.OpenApi.OData.Reader/Generator/OpenApiParameterGenerator.cs
+++ b/src/Microsoft.OpenApi.OData.Reader/Generator/OpenApiParameterGenerator.cs
@@ -81,7 +81,8 @@ public static IList<OpenApiParameter> CreateParameters(this ODataContext context
                     }
                 }                
 
-                OpenApiParameter parameter;                
+                OpenApiParameter parameter;
+                bool isOptionalParameter = edmParameter is IEdmOptionalParameter;
                 if (edmParameter.Type.IsStructured() ||
                     edmParameter.Type.IsCollection())
                 {
@@ -121,7 +122,6 @@ public static IList<OpenApiParameter> CreateParameters(this ODataContext context
                 else
                 {
                     // Primitive parameters use the same type mapping as described for primitive properties.
-                    bool isOptionalParameter = edmParameter is IEdmOptionalParameter;
                     parameter = new OpenApiParameter
                     {
                         Name = parameterNameMapping == null ? edmParameter.Name : parameterNameMapping[edmParameter.Name],
@@ -134,7 +134,9 @@ public static IList<OpenApiParameter> CreateParameters(this ODataContext context
                 if (parameterNameMapping != null)
                 {
                     var quote = edmParameter.Type.Definition.ShouldPathParameterBeQuoted(context.Settings) ? "'" : string.Empty;
-                    parameter.Description = $"Usage: {edmParameter.Name}={quote}{{{parameterNameMapping[edmParameter.Name]}}}{quote}";
+                    parameter.Description = isOptionalParameter
+                        ? $"Usage: {edmParameter.Name}={quote}@{parameterNameMapping[edmParameter.Name]}{quote}"
+                        : $"Usage: {edmParameter.Name}={quote}{{{parameterNameMapping[edmParameter.Name]}}}{quote}";
                 }
 
                 parameters.Add(parameter);
diff --git a/test/Microsoft.OpenAPI.OData.Reader.Tests/Edm/ODataOperationSegmentTests.cs b/test/Microsoft.OpenAPI.OData.Reader.Tests/Edm/ODataOperationSegmentTests.cs
index a571bdb5..2030cd61 100644
--- a/test/Microsoft.OpenAPI.OData.Reader.Tests/Edm/ODataOperationSegmentTests.cs
+++ b/test/Microsoft.OpenAPI.OData.Reader.Tests/Edm/ODataOperationSegmentTests.cs
@@ -4,7 +4,6 @@
 // ------------------------------------------------------------
 
 using System;
-using System.Runtime.CompilerServices;
 using Microsoft.OData.Edm;
 using Xunit;
 
@@ -74,10 +73,10 @@ public void GetPathItemNameReturnsCorrectActionLiteral(bool unqualifiedCall, boo
         }
 
         [Theory]
-        [InlineData(true, true, "MyFunction(param={param})")]
-        [InlineData(true, false, "MyFunction(entity={entity},param={param})")]
-        [InlineData(false, true, "NS.MyFunction(param={param})")]
-        [InlineData(false, false, "NS.MyFunction(entity={entity},param={param})")]
+        [InlineData(true, true, "MyFunction(param={param},param2=@param2)")]
+        [InlineData(true, false, "MyFunction(entity={entity},param={param},param2=@param2)")]
+        [InlineData(false, true, "NS.MyFunction(param={param},param2=@param2)")]
+        [InlineData(false, false, "NS.MyFunction(entity={entity},param={param},param2=@param2)")]
         public void GetPathItemNameReturnsCorrectFunctionLiteral(bool unqualifiedCall, bool isBound, string expected)
         {
             // Arrange & Act
@@ -85,6 +84,7 @@ public void GetPathItemNameReturnsCorrectFunctionLiteral(bool unqualifiedCall, b
             IEdmTypeReference parameterType = EdmCoreModel.Instance.GetPrimitive(EdmPrimitiveTypeKind.Boolean, isNullable: false);
             EdmFunction boundFunction = BoundFunction("MyFunction", isBound, entityTypeReference);
             boundFunction.AddParameter("param", parameterType);
+            boundFunction.AddOptionalParameter("param2", parameterType);
 
             var segment = new ODataOperationSegment(boundFunction);
             OpenApiConvertSettings settings = new OpenApiConvertSettings
@@ -97,10 +97,10 @@ public void GetPathItemNameReturnsCorrectFunctionLiteral(bool unqualifiedCall, b
         }
 
         [Theory]
-        [InlineData(true, true, "{param}")]
-        [InlineData(true, false, "NS.MyFunction(param='{param}')")]
-        [InlineData(false, true, "NS.MyFunction(param='{param}')")]
-        [InlineData(false, false, "NS.MyFunction(param='{param}')")]
+        [InlineData(true, true, "{param2}")]
+        [InlineData(true, false, "NS.MyFunction(param='{param}',param2='@param2')")]
+        [InlineData(false, true, "NS.MyFunction(param='{param}',param2='@param2')")]
+        [InlineData(false, false, "NS.MyFunction(param='{param}',param2='@param2')")]
         public void GetPathItemNameReturnsCorrectFunctionLiteralForEscapedFunction(bool isEscapedFunction, bool enableEscapeFunctionCall, string expected)
         {
             // Arrange & Act
@@ -108,6 +108,7 @@ public void GetPathItemNameReturnsCorrectFunctionLiteralForEscapedFunction(bool
             IEdmTypeReference parameterType = EdmCoreModel.Instance.GetPrimitive(EdmPrimitiveTypeKind.String, isNullable: false);
             EdmFunction boundFunction = BoundFunction("MyFunction", true, entityTypeReference);
             boundFunction.AddParameter("param", parameterType);
+            boundFunction.AddOptionalParameter("param2", parameterType);
 
             var segment = new ODataOperationSegment(boundFunction, isEscapedFunction);
             OpenApiConvertSettings settings = new OpenApiConvertSettings
@@ -121,10 +122,10 @@ public void GetPathItemNameReturnsCorrectFunctionLiteralForEscapedFunction(bool
         }
 
         [Theory]
-        [InlineData(true, true, "{param}:")]
-        [InlineData(true, false, "NS.MyFunction(param='{param}')")]
-        [InlineData(false, true, "NS.MyFunction(param='{param}')")]
-        [InlineData(false, false, "NS.MyFunction(param='{param}')")]
+        [InlineData(true, true, "{param2}:")]
+        [InlineData(true, false, "NS.MyFunction(param='{param}',param2='@param2')")]
+        [InlineData(false, true, "NS.MyFunction(param='{param}',param2='@param2')")]
+        [InlineData(false, false, "NS.MyFunction(param='{param}',param2='@param2')")]
         public void GetPathItemNameReturnsCorrectFunctionLiteralForEscapedComposableFunction(bool isEscapedFunction, bool enableEscapeFunctionCall, string expected)
         {
             // Arrange & Act
@@ -132,6 +133,7 @@ public void GetPathItemNameReturnsCorrectFunctionLiteralForEscapedComposableFunc
             IEdmTypeReference parameterType = EdmCoreModel.Instance.GetPrimitive(EdmPrimitiveTypeKind.String, isNullable: false);
             EdmFunction boundFunction = BoundFunction("MyFunction", true, entityTypeReference, true);
             boundFunction.AddParameter("param", parameterType);
+            boundFunction.AddOptionalParameter("param2", parameterType);
 
             var segment = new ODataOperationSegment(boundFunction, isEscapedFunction);
             OpenApiConvertSettings settings = new OpenApiConvertSettings