diff --git a/ToSic.Eav.WebApi/Dto/ContentTypeDto.cs b/ToSic.Eav.WebApi/Dto/ContentTypeDto.cs
index dfa35aed1..fa368e247 100644
--- a/ToSic.Eav.WebApi/Dto/ContentTypeDto.cs
+++ b/ToSic.Eav.WebApi/Dto/ContentTypeDto.cs
@@ -1,9 +1,10 @@
 using System.Collections.Generic;
+using Newtonsoft.Json;
 using ToSic.Eav.WebApi.Security;
 
 namespace ToSic.Eav.WebApi.Dto
 {
-    public class ContentTypeDto: IdNameDto
+    public class ContentTypeDto: IdNameDto, IReadOnlyDto
     {
         public string Label { get; set; }
         public string StaticName { get; set; }
@@ -17,5 +18,10 @@ public class ContentTypeDto: IdNameDto
         public IDictionary<string, object> Properties { get; set; }
 
         public HasPermissionsDto Permissions { get; set; }
+
+        //[JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
+        public bool? IsReadOnly { get; set; }
+
+        public string IsReadOnlyReason { get; set; }
     }
 }
\ No newline at end of file
diff --git a/ToSic.Eav.WebApi/Dto/ContentTypeFieldDto.cs b/ToSic.Eav.WebApi/Dto/ContentTypeFieldDto.cs
index e819bc1fc..18610cc65 100644
--- a/ToSic.Eav.WebApi/Dto/ContentTypeFieldDto.cs
+++ b/ToSic.Eav.WebApi/Dto/ContentTypeFieldDto.cs
@@ -5,7 +5,7 @@
 
 namespace ToSic.Eav.WebApi.Dto
 {
-    public class ContentTypeFieldDto
+    public class ContentTypeFieldDto: IReadOnlyDto
     {
         public int Id { get; set; }
         public int SortOrder { get; set; }
@@ -34,5 +34,8 @@ public class ContentTypeFieldDto
         /// New in v12.01
         /// </remarks>
         public bool HasFormulas { get; set; }
+
+        public bool? IsReadOnly { get; set; }
+        public string IsReadOnlyReason { get; set; }
     }
 }
diff --git a/ToSic.Eav.WebApi/Dto/IReadOnlyDto.cs b/ToSic.Eav.WebApi/Dto/IReadOnlyDto.cs
new file mode 100644
index 000000000..c6f704d2b
--- /dev/null
+++ b/ToSic.Eav.WebApi/Dto/IReadOnlyDto.cs
@@ -0,0 +1,16 @@
+using Newtonsoft.Json;
+
+namespace ToSic.Eav.WebApi.Dto
+{
+    /// <summary>
+    /// Extends common DTOs to inform about it being read-only, and why
+    /// </summary>
+    public interface IReadOnlyDto
+    {
+        [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
+        bool? IsReadOnly { get; set; }
+
+        [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
+        string IsReadOnlyReason { get; set; }
+    }
+}