diff --git a/function_app.py b/function_app.py
index 6ebeffe..c0e9d96 100644
--- a/function_app.py
+++ b/function_app.py
@@ -7,8 +7,24 @@
 from bson import ObjectId
 from datetime import datetime
 
+# Read flag from environment variables
+ENABLE_OBJECTID_CONVERSION = os.getenv("ENABLE_OBJECTID_CONVERSION", "true").lower() == "true"
+
 app = func.FunctionApp(http_auth_level=func.AuthLevel.FUNCTION)
 
+def convert_objectid(document):
+    """Recursively convert ObjectIds to strings."""
+    if isinstance(document, list):
+        return [convert_objectid(d) for d in document]
+    elif isinstance(document, dict):
+        return {
+            k: str(v) if ENABLE_OBJECTID_CONVERSION and isinstance(v, ObjectId)
+            else convert_objectid(v)
+            for k, v in document.items()
+        }
+    else:
+        return document
+
 def connect_to_mongodb():
     conn_str = os.environ.get("MONGODBATLAS_CLUSTER_CONNECTIONSTRING")
     if not conn_str:
@@ -132,6 +148,8 @@ def mongodb_dataapi_replace(req: func.HttpRequest) -> func.HttpResponse:
         else:
             return error_response("Not a valid operation")
 
+        result = convert_objectid(result)
+        
         return success_response(result)
 
     except Exception as e:
@@ -141,3 +159,4 @@ def mongodb_dataapi_replace(req: func.HttpRequest) -> func.HttpResponse:
     finally:
         if client:
             client.close()
+