<PackageReference Include="NJsonSchema" Version="11.0.0-preview005" />

IJsonSchemaExtensionDataAttribute

Interface to add an extension data property to a class or property, implementation needs to inherit from System.Attribute.
using System.Collections.Generic; using System.Runtime.CompilerServices; namespace NJsonSchema.Annotations { [System.Runtime.CompilerServices.NullableContext(1)] public interface IJsonSchemaExtensionDataAttribute { IReadOnlyDictionary<string, object> ExtensionData { get; } } }