diff --git a/src/ModelContextProtocol/McpJsonUtilities.cs b/src/ModelContextProtocol/McpJsonUtilities.cs
index ca9748437..7e0b79746 100644
--- a/src/ModelContextProtocol/McpJsonUtilities.cs
+++ b/src/ModelContextProtocol/McpJsonUtilities.cs
@@ -78,7 +78,11 @@ internal static bool IsValidMcpToolSchema(JsonElement element)
     // Keep in sync with CreateDefaultOptions above.
     [JsonSourceGenerationOptions(JsonSerializerDefaults.Web,
         DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
-        NumberHandling = JsonNumberHandling.AllowReadingFromString)]
+        NumberHandling = JsonNumberHandling.AllowReadingFromString
+#if NET9_0_OR_GREATER
+        ,UseStringEnumConverter = true
+#endif
+    )]
     
     // JSON-RPC
     [JsonSerializable(typeof(JsonRpcMessage))]