diff --git a/src/llamafactory/data/formatter.py b/src/llamafactory/data/formatter.py
index 0e51acae..99a4a8b4 100644
--- a/src/llamafactory/data/formatter.py
+++ b/src/llamafactory/data/formatter.py
@@ -113,7 +113,7 @@ class FunctionFormatter(Formatter):
                 functions.append((tool_call["name"], json.dumps(tool_call["arguments"], ensure_ascii=False)))
 
         except json.JSONDecodeError:
-            raise RuntimeError("Invalid JSON format in function message: {}".format(content))
+            raise RuntimeError("Invalid JSON format in function message: {}".format(str([content])))  # flat string
 
         elements = []
         for name, arguments in functions:
@@ -141,7 +141,7 @@ class ToolFormatter(Formatter):
             tools = json.loads(content)
             return [self.tool_utils.tool_formatter(tools) if len(tools) != 0 else ""]
         except json.JSONDecodeError:
-            raise RuntimeError("Invalid JSON format in tool description: {}".format(content))
+            raise RuntimeError("Invalid JSON format in tool description: {}".format(str([content])))  # flat string
 
     @override
     def extract(self, content: str) -> Union[str, List["FunctionCall"]]: