remove placeholder error message (#20340)

libs/core/langchain_core/messages/ai.py

@@ -124,7 +124,7 @@ class AIMessageChunk(AIMessage, BaseMessageChunk):
                         name=chunk["name"],
                         args=chunk["args"],
                         id=chunk["id"],
-                        error="Malformed args.",
+                        error=None,
                     )
                 )
         values["tool_calls"] = tool_calls

libs/core/langchain_core/messages/tool.py

@@ -149,7 +149,7 @@ def default_tool_parser(
                         name=function_name,
                         args=tool_call["function"]["arguments"],
                         id=tool_call.get("id"),
-                        error="Malformed args.",
+                        error=None,
                     )
                 )
     return tool_calls, invalid_tool_calls

libs/core/tests/unit_tests/messages/test_ai.py

@@ -53,7 +53,7 @@ def test_serdes_message_chunk() -> None:
                     "name": "foobad",
                     "args": "blah",
                     "id": "booz",
-                    "error": "Malformed args.",
+                    "error": None,
                 }
             ],
             "tool_call_chunks": [

libs/core/tests/unit_tests/test_messages.py

@@ -306,8 +306,8 @@ def test_message_chunk_to_message() -> None:
             {"name": "tool2", "args": {}, "id": "2"},
         ],
         invalid_tool_calls=[
-            {"name": "tool3", "args": None, "id": "3", "error": "Malformed args."},
-            {"name": "tool4", "args": "abc", "id": "4", "error": "Malformed args."},
+            {"name": "tool3", "args": None, "id": "3", "error": None},
+            {"name": "tool4", "args": "abc", "id": "4", "error": None},
         ],
     )
     assert message_chunk_to_message(chunk) == expected