diff --git a/backend-java/src/main/java/com/tasteby/util/JsonUtil.java b/backend-java/src/main/java/com/tasteby/util/JsonUtil.java
index 373afb8..8f34b69 100644
--- a/backend-java/src/main/java/com/tasteby/util/JsonUtil.java
+++ b/backend-java/src/main/java/com/tasteby/util/JsonUtil.java
@@ -53,7 +53,8 @@ public final class JsonUtil {
         try {
             return MAPPER.readValue(json, new TypeReference<>() {});
         } catch (Exception e) {
-            return Collections.emptyMap();
+            // Plain text or malformed JSON (e.g. Python-style single quotes) → wrap as {"text": "..."}
+            return Map.of("text", json.trim());
         }
     }
 
@@ -74,6 +75,24 @@ public final class JsonUtil {
         return rows.stream().map(JsonUtil::lowerKeys).collect(Collectors.toList());
     }
 
+    /**
+     * Normalize evaluation to a valid JSON object string (e.g. {"text":"..."}).
+     * Plain text is wrapped, already-valid JSON is returned as-is, and text is truncated to maxLen.
+     */
+    public static String normalizeEvaluation(String eval, int maxLen) {
+        if (eval == null || eval.isBlank()) return null;
+        String trimmed = eval.trim();
+        if (trimmed.startsWith("{")) return trimmed;
+        if (trimmed.length() > maxLen) {
+            trimmed = trimmed.substring(0, maxLen);
+        }
+        return toJson(Map.of("text", trimmed));
+    }
+
+    public static String normalizeEvaluation(String eval) {
+        return normalizeEvaluation(eval, 300);
+    }
+
     public static String toJson(Object value) {
         try {
             return MAPPER.writeValueAsString(value);