diff --git a/aiola/clients/stt/client.py b/aiola/clients/stt/client.py
index a88c978..19acbce 100644
--- a/aiola/clients/stt/client.py
+++ b/aiola/clients/stt/client.py
@@ -63,13 +63,17 @@ def _build_query_and_headers(
         query = {
             "execution_id": execution_id,
             "flow_id": resolved_workflow_id,
-            "lang_code": lang_code or "en",
             "time_zone": time_zone or "UTC",
-            "keywords": json.dumps(keywords or {}),
-            "tasks_config": json.dumps(tasks_config or {}),
             "x-aiola-api-token": access_token,
         }
 
+        if lang_code is not None:
+            query["lang_code"] = lang_code
+        if keywords is not None:
+            query["keywords"] = json.dumps(keywords)
+        if tasks_config is not None:
+            query["tasks_config"] = json.dumps(tasks_config)
+
         headers = {
             "Authorization": f"Bearer {access_token}",
         }
diff --git a/aiola/types.py b/aiola/types.py
index 9d8b883..0978fc3 100644
--- a/aiola/types.py
+++ b/aiola/types.py
@@ -3,7 +3,7 @@
 import enum
 from collections.abc import Mapping
 from dataclasses import dataclass
-from typing import IO, Union
+from typing import IO, Any, Union
 
 from .constants import DEFAULT_AUTH_BASE_URL, DEFAULT_BASE_URL, DEFAULT_HTTP_TIMEOUT, DEFAULT_WORKFLOW_ID
 
@@ -46,16 +46,7 @@ def __post_init__(self) -> None:
 class LiveEvents(str, enum.Enum):
     Transcript = "transcript"
     Translation = "translation"
-    SentimentAnalysis = "sentiment_analysis"
-    Summarization = "summarization"
-    TopicDetection = "topic_detection"
-    ContentModeration = "content_moderation"
-    AutoChapters = "auto_chapters"
-    FormFilling = "form_filling"
-    EntityDetection = "entity_detection"
-    EntityDetectionFromList = "entity_detection_from_list"
-    KeyPhrases = "key_phrases"
-    PiiRedaction = "pii_redaction"
+    Structured = "structured"
     Error = "error"
     Disconnect = "disconnect"
     Connect = "connect"
@@ -115,6 +106,13 @@ def from_dict(cls, data: dict) -> TranscriptionResponse:
         )
 
 
+@dataclass
+class StructuredResponse:
+    """Response from structured API."""
+
+    results: dict[str, Any]
+
+
 @dataclass
 class SessionCloseResponse:
     """Response from session close API."""
@@ -137,40 +135,9 @@ class TranslationPayload:
     dst_lang_code: str
 
 
-@dataclass
-class EntityDetectionFromListPayload:
-    entity_list: list[str]
-
-
-@dataclass
-class _EmptyPayload:
-    pass
-
-
-EntityDetectionPayload = _EmptyPayload
-KeyPhrasesPayload = _EmptyPayload
-PiiRedactionPayload = _EmptyPayload
-SentimentAnalysisPayload = _EmptyPayload
-SummarizationPayload = _EmptyPayload
-TopicDetectionPayload = _EmptyPayload
-ContentModerationPayload = _EmptyPayload
-AutoChaptersPayload = _EmptyPayload
-FormFillingPayload = _EmptyPayload
-
-
 @dataclass
 class TasksConfig:
-    FORM_FILLING: FormFillingPayload | None = None
     TRANSLATION: TranslationPayload | None = None
-    ENTITY_DETECTION: EntityDetectionPayload | None = None
-    ENTITY_DETECTION_FROM_LIST: EntityDetectionFromListPayload | None = None
-    KEY_PHRASES: KeyPhrasesPayload | None = None
-    PII_REDACTION: PiiRedactionPayload | None = None
-    SENTIMENT_ANALYSIS: SentimentAnalysisPayload | None = None
-    SUMMARIZATION: SummarizationPayload | None = None
-    TOPIC_DETECTION: TopicDetectionPayload | None = None
-    CONTENT_MODERATION: ContentModerationPayload | None = None
-    AUTO_CHAPTERS: AutoChaptersPayload | None = None
 
 
 FileContent = Union[IO[bytes], bytes, str]
diff --git a/tests/unit/stt/test_stt_client.py b/tests/unit/stt/test_stt_client.py
index 8780cbc..feca5de 100644
--- a/tests/unit/stt/test_stt_client.py
+++ b/tests/unit/stt/test_stt_client.py
@@ -326,7 +326,7 @@ def test_stt_stream_with_empty_tasks_config(patch_dummy_socket):
 
 
 def test_stt_stream_with_no_tasks_config(patch_dummy_socket):
-    """``SttClient.stream`` handles None tasks_config properly."""
+    """``SttClient.stream`` handles None tasks_config properly by not including it in URL."""
 
     client = AiolaClient(api_key="secret-key", base_url="https://speech.example")
 
@@ -341,15 +341,14 @@ def test_stt_stream_with_no_tasks_config(patch_dummy_socket):
     # Access the underlying socket to validate connection parameters
     sio = connection._sio
 
-    # Verify None tasks_config is serialized as empty JSON object
+    # Verify None tasks_config is not included in URL
     kwargs = sio.connect_kwargs
     url = kwargs["url"]
     parsed = urllib.parse.urlparse(url)
     query = urllib.parse.parse_qs(parsed.query)
 
-    tasks_config_json = query["tasks_config"][0]
-    parsed_tasks_config = json.loads(tasks_config_json)
-    assert parsed_tasks_config == {}
+    # tasks_config should not be present when None
+    assert "tasks_config" not in query
 
 
 def test_stt_stream_with_all_tasks_config(patch_dummy_socket):