diff --git a/examples/rag_pipeline.py b/examples/rag_pipeline.py
index 2f26ff052..daf4014fc 100644
--- a/examples/rag_pipeline.py
+++ b/examples/rag_pipeline.py
@@ -19,15 +19,15 @@ QUESTION = "What are key qualities to be a good writer?"
 TRAVEL_DOC_PATH = EXAMPLE_DATA_PATH / "rag/travel.txt"
 TRAVEL_QUESTION = "What does Bob like?"
 
-LLM_TIP = "If you not sure, just answer I don't know"
+LLM_TIP = "If you not sure, just answer I don't know."
 
 
 class Player(BaseModel):
-    """To demonstrate rag add objs"""
+    """To demonstrate rag add objs."""
 
     name: str = ""
-    goal: str = "Win The 100-meter Sprint"
-    tool: str = "Red Bull Energy Drink"
+    goal: str = "Win The 100-meter Sprint."
+    tool: str = "Red Bull Energy Drink."
 
     def rag_key(self) -> str:
         """For search"""
@@ -108,7 +108,7 @@ class RAGExample:
         self._print_title("RAG Add Objs")
 
         player = Player(name="Mike")
-        question = f"{player.rag_key()}{LLM_TIP}"
+        question = f"{player.rag_key()}"
 
         print("[Before add objs]")
         await self._retrieve_and_print(question)
diff --git a/metagpt/rag/engines/simple.py b/metagpt/rag/engines/simple.py
index 4d47c7084..22351d8fd 100644
--- a/metagpt/rag/engines/simple.py
+++ b/metagpt/rag/engines/simple.py
@@ -22,7 +22,6 @@ from llama_index.core.schema import (
     NodeWithScore,
     QueryBundle,
     QueryType,
-    TextNode,
     TransformComponent,
 )
 
@@ -35,7 +34,12 @@ from metagpt.rag.factories import (
 )
 from metagpt.rag.interface import RAGObject
 from metagpt.rag.retrievers.base import ModifiableRAGRetriever
-from metagpt.rag.schema import BaseIndexConfig, BaseRankerConfig, BaseRetrieverConfig
+from metagpt.rag.schema import (
+    BaseIndexConfig,
+    BaseRankerConfig,
+    BaseRetrieverConfig,
+    ObjectNode,
+)
 from metagpt.utils.common import import_class
 
 
@@ -149,18 +153,9 @@ class SimpleEngine(RetrieverQueryEngine):
         """Adds objects to the retriever, storing each object's original form in metadata for future reference."""
         self._ensure_retriever_modifiable()
 
-        nodes = [TextNode(text=obj.rag_key(), metadata=self._get_obj_metadata(obj)) for obj in objs]
+        nodes = [ObjectNode(text=obj.rag_key(), metadata=ObjectNode.get_obj_metadata(obj)) for obj in objs]
         self._save_nodes(nodes)
 
-    def _get_obj_metadata(self, obj: RAGObject) -> dict:
-        metadata = {
-            "is_obj": True,
-            "obj_dict": obj.model_dump(),
-            "obj_cls_name": obj.__class__.__name__,
-            "obj_mod_name": obj.__class__.__module__,
-        }
-        return metadata
-
     def _ensure_retriever_modifiable(self):
         if not isinstance(self.retriever, ModifiableRAGRetriever):
             raise TypeError(f"the retriever is not modifiable: {type(self.retriever)}")
diff --git a/metagpt/rag/schema.py b/metagpt/rag/schema.py
index 35e16e286..9657ae846 100644
--- a/metagpt/rag/schema.py
+++ b/metagpt/rag/schema.py
@@ -5,8 +5,11 @@ from typing import Any, Union
 
 from llama_index.core.embeddings import BaseEmbedding
 from llama_index.core.indices.base import BaseIndex
+from llama_index.core.schema import TextNode
 from pydantic import BaseModel, ConfigDict, Field
 
+from metagpt.rag.interface import RAGObject
+
 
 class BaseRetrieverConfig(BaseModel):
     """Common config for retrievers.
@@ -84,3 +87,27 @@ class ChromaIndexConfig(VectorIndexConfig):
     """Config for chroma-based index."""
 
     collection_name: str = Field(default="metagpt", description="The name of the collection.")
+
+
+class ObjectNodeMetadata(BaseModel):
+    """Metadata of ObjectNode."""
+
+    is_obj: bool = Field(default=True)
+    obj_dict: dict = Field(..., description="Inplement rag.interface.RAGObject.model_dump(), e.g. obj.model_dump()")
+    obj_cls_name: str = Field(..., description="The class name of object, e.g. obj.__class__.__name__")
+    obj_mod_name: str = Field(..., description="The module name of class, e.g. obj.__class__.__module__")
+
+
+class ObjectNode(TextNode):
+    """RAG add object."""
+
+    def __init__(self, **kwargs):
+        super().__init__(**kwargs)
+        self.excluded_llm_metadata_keys = list(ObjectNodeMetadata.model_fields.keys())
+
+    @staticmethod
+    def get_obj_metadata(obj: RAGObject) -> dict:
+        metadata = ObjectNodeMetadata(
+            obj_dict=obj.model_dump(), obj_cls_name=obj.__class__.__name__, obj_mod_name=obj.__class__.__module__
+        )
+        return metadata.model_dump()
diff --git a/tests/metagpt/rag/engines/test_simple.py b/tests/metagpt/rag/engines/test_simple.py
index 1d1ddad12..60e72e422 100644
--- a/tests/metagpt/rag/engines/test_simple.py
+++ b/tests/metagpt/rag/engines/test_simple.py
@@ -1,6 +1,6 @@
 import pytest
 from llama_index.core import VectorStoreIndex
-from llama_index.core.schema import TextNode
+from llama_index.core.schema import NodeWithScore, TextNode
 
 from metagpt.rag.engines import SimpleEngine
 from metagpt.rag.retrievers.base import ModifiableRAGRetriever
@@ -97,7 +97,8 @@ class TestSimpleEngine:
         mock_super_aretrieve = mocker.patch(
             "metagpt.rag.engines.simple.RetrieverQueryEngine.aretrieve", new_callable=mocker.AsyncMock
         )
-        mock_super_aretrieve.return_value = ["node_with_score"]
+        nodes = [NodeWithScore(node=TextNode())]
+        mock_super_aretrieve.return_value = nodes
 
         # Setup
         engine = SimpleEngine(retriever=mocker.MagicMock())
@@ -109,7 +110,7 @@ class TestSimpleEngine:
         # Assertions
         mock_query_bundle.assert_called_once_with(test_query)
         mock_super_aretrieve.assert_called_once_with("query_bundle")
-        assert result == ["node_with_score"]
+        assert result == nodes
 
     def test_add_docs(self, mocker):
         # Mock
@@ -157,4 +158,4 @@ class TestSimpleEngine:
         assert mock_retriever.add_nodes.call_count == 1
         for node in mock_retriever.add_nodes.call_args[0][0]:
             assert isinstance(node, TextNode)
-            assert "obj" in node.metadata
+            assert "obj_dict" in node.metadata