diff --git a/tools/X10D.MetaServices/Assembly.cs b/tools/X10D.MetaServices/Assembly.cs
new file mode 100644
index 0000000..274a45a
--- /dev/null
+++ b/tools/X10D.MetaServices/Assembly.cs
@@ -0,0 +1,4 @@
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("X10D")]
+[assembly: InternalsVisibleTo("SourceGenerator")]
diff --git a/tools/X10D.MetaServices/AutoOverloadAttribute.cs b/tools/X10D.MetaServices/AutoOverloadAttribute.cs
index 5630c84..382e63e 100644
--- a/tools/X10D.MetaServices/AutoOverloadAttribute.cs
+++ b/tools/X10D.MetaServices/AutoOverloadAttribute.cs
@@ -1,6 +1,6 @@
 namespace X10D.MetaServices;
 
 [AttributeUsage(AttributeTargets.Method, Inherited = false)]
-public sealed class AutoOverloadAttribute : Attribute
+internal sealed class AutoOverloadAttribute : Attribute
 {
 }
diff --git a/tools/X10D.MetaServices/OverloadTypeAttribute.cs b/tools/X10D.MetaServices/OverloadTypeAttribute.cs
index d938a5b..0fdde1a 100644
--- a/tools/X10D.MetaServices/OverloadTypeAttribute.cs
+++ b/tools/X10D.MetaServices/OverloadTypeAttribute.cs
@@ -1,7 +1,7 @@
 namespace X10D.MetaServices;
 
 [AttributeUsage(AttributeTargets.Method | AttributeTargets.Parameter | AttributeTargets.ReturnValue, Inherited = false)]
-public sealed class OverloadTypeAttribute : Attribute
+internal sealed class OverloadTypeAttribute : Attribute
 {
     /// <summary>
     ///     Initializes a new instance of the <see cref="OverloadTypeAttribute"/> class.