diff --git a/src/promptflow/promptflow/_core/metric_logger.py b/src/promptflow/promptflow/_core/metric_logger.py
index b17891606a4..e5c14f2ceed 100644
--- a/src/promptflow/promptflow/_core/metric_logger.py
+++ b/src/promptflow/promptflow/_core/metric_logger.py
@@ -45,6 +45,15 @@ def remove_metric_logger(self, logger_func: Callable):
 
 
 def log_metric(key, value, variant_id=None):
+    """Log a metric for current promptflow run.
+
+    :param key: Metric name.
+    :type key: str
+    :param value: Metric value.
+    :type value: float
+    :param variant_id: Variant id for the metric.
+    :type variant_id: str
+    """
     MetricLoggerManager.get_instance().log_metric(key, value, variant_id)
 
 
diff --git a/src/promptflow/promptflow/_core/tool.py b/src/promptflow/promptflow/_core/tool.py
index a65b0b39d5d..48ab30db4dd 100644
--- a/src/promptflow/promptflow/_core/tool.py
+++ b/src/promptflow/promptflow/_core/tool.py
@@ -7,7 +7,7 @@
 import logging
 from abc import ABC
 from enum import Enum
-from typing import Optional
+from typing import Callable, Optional
 
 module_logger = logging.getLogger(__name__)
 
@@ -39,7 +39,15 @@ def active_instance(cls) -> Optional["ToolInvoker"]:
         return cls._active_tool_invoker
 
 
-def tool(f):
+def tool(f: Callable) -> Callable:
+    """Decorator for tool functions. The decorated function will be registered as a tool and can be used in a flow.
+
+    :param f: The tool function.
+    :type f: Callable
+    :return: The decorated function.
+    :rtype: Callable
+    """
+
     @functools.wraps(f)
     def new_f(*args, **kwargs):
         tool_invoker = ToolInvoker.active_instance()
diff --git a/src/promptflow/promptflow/_sdk/_pf_client.py b/src/promptflow/promptflow/_sdk/_pf_client.py
index 385716ddfe8..ee7107c328f 100644
--- a/src/promptflow/promptflow/_sdk/_pf_client.py
+++ b/src/promptflow/promptflow/_sdk/_pf_client.py
@@ -101,6 +101,7 @@ def stream(self, run: Union[str, Run]) -> Run:
         :param run: Run object or name of the run.
         :type run: Union[str, ~promptflow.sdk.entities.Run]
         :return: flow run info.
+        :rtype: ~promptflow.sdk.entities.Run
         """
         return self.runs.stream(run)
 
@@ -134,15 +135,17 @@ def visualize(self, runs: Union[List[str], List[Run]]) -> None:
 
     @property
     def runs(self) -> RunOperations:
+        """Run operations that can manage runs."""
         return self._runs
 
     @property
     def connections(self) -> ConnectionOperations:
+        """Connection operations that can manage connections."""
         return self._connections
 
     @property
     def flows(self) -> FlowOperations:
-        """Operations on the flow, such as test/debug the flow, chat with chat flow."""
+        """Operations on the flow that can manage flows."""
         return self._flows
 
     def test(
@@ -154,7 +157,7 @@ def test(
         node: str = None,
         environment_variables: dict = None,
     ) -> dict:
-        """Test flow or node
+        """Test flow or node.
 
         :param flow: path to flow directory to test
         :type flow: Union[str, PathLike]
diff --git a/src/promptflow/promptflow/_sdk/entities/_connection.py b/src/promptflow/promptflow/_sdk/entities/_connection.py
index f7536493736..0716d2f17f1 100644
--- a/src/promptflow/promptflow/_sdk/entities/_connection.py
+++ b/src/promptflow/promptflow/_sdk/entities/_connection.py
@@ -44,6 +44,20 @@
 
 
 class _Connection(YAMLTranslatableMixin):
+    """A connection entity that stores the connection information.
+
+    :param name: Connection name
+    :type name: str
+    :param type: Possible values include: "OpenAI", "AzureOpenAI", "Custom".
+    :type type: str
+    :param module: The module of connection class, used for execution.
+    :type module: str
+    :param configs: The configs kv pairs.
+    :type configs: Dict[str, str]
+    :param secrets: The secrets kv pairs.
+    :type secrets: Dict[str, str]
+    """
+
     TYPE = ConnectionType._NOT_SET
 
     def __init__(
@@ -54,13 +68,6 @@ def __init__(
         secrets: Dict[str, str] = None,
         **kwargs,
     ):
-        """
-        :param name: Connection name
-        :param type: Possible values include: "OpenAI", "AzureOpenAI", "Custom".
-        :param module: The module of connection class, used for execution.
-        :param configs: The configs kv pairs.
-        :param secrets: The secrets kv pairs.
-        """
         self.name = name
         self.type = self.TYPE
         self.class_name = f"{self.TYPE.value}Connection"  # The type in executor connection dict
@@ -290,14 +297,18 @@ def api_key(self, value):
 
 
 class AzureOpenAIConnection(_StrongTypeConnection):
-    """
-    Azure Open AI connection.
+    """Azure Open AI connection.
 
     :param api_key: The api key.
+    :type api_key: str
     :param api_base: The api base.
+    :type api_base: str
     :param api_type: The api type, default "azure".
+    :type api_type: str
     :param api_version: The api version, default "2023-07-01-preview".
+    :type api_version: str
     :param name: Connection name.
+    :type name: str
     """
 
     TYPE = ConnectionType.AZURE_OPEN_AI
@@ -345,12 +356,14 @@ def api_version(self, value):
 
 
 class OpenAIConnection(_StrongTypeConnection):
-    """
-    Open AI connection.
+    """Open AI connection.
 
     :param api_key: The api key.
+    :type api_key: str
     :param organization: Optional. The unique identifier for your organization which can be used in API requests.
+    :type organization: str
     :param name: Connection name.
+    :type name: str
     """
 
     TYPE = ConnectionType.OPEN_AI
@@ -376,11 +389,12 @@ def organization(self, value):
 
 
 class SerpConnection(_StrongTypeConnection):
-    """
-    Serp connection.
+    """Serp connection.
 
     :param api_key: The api key.
+    :type api_key: str
     :param name: Connection name.
+    :type name: str
     """
 
     TYPE = ConnectionType.SERP
@@ -412,12 +426,14 @@ def api_base(self, value):
 
 
 class QdrantConnection(_EmbeddingStoreConnection):
-    """
-    Qdrant connection.
+    """Qdrant connection.
 
     :param api_key: The api key.
+    :type api_key: str
     :param api_base: The api base.
+    :type api_base: str
     :param name: Connection name.
+    :type name: str
     """
 
     TYPE = ConnectionType.QDRANT
@@ -428,12 +444,14 @@ def _get_schema_cls(cls):
 
 
 class WeaviateConnection(_EmbeddingStoreConnection):
-    """
-    Weaviate connection.
+    """Weaviate connection.
 
     :param api_key: The api key.
+    :type api_key: str
     :param api_base: The api base.
+    :type api_base: str
     :param name: Connection name.
+    :type name: str
     """
 
     TYPE = ConnectionType.WEAVIATE
@@ -444,13 +462,16 @@ def _get_schema_cls(cls):
 
 
 class CognitiveSearchConnection(_StrongTypeConnection):
-    """
-    Cognitive Search connection.
+    """Cognitive Search connection.
 
     :param api_key: The api key.
+    :type api_key: str
     :param api_base: The api base.
+    :type api_base: str
     :param api_version: The api version, default "2023-07-01-Preview".
+    :type api_version: str
     :param name: Connection name.
+    :type name: str
     """
 
     TYPE = ConnectionType.COGNITIVE_SEARCH
@@ -490,10 +511,15 @@ class AzureContentSafetyConnection(_StrongTypeConnection):
     Azure Content Safety connection.
 
     :param api_key: The api key.
+    :type api_key: str
     :param endpoint: The api endpoint.
+    :type endpoint: str
     :param api_version: The api version, default "2023-04-30-preview".
+    :type api_version: str
     :param api_type: The api type, default "Content Safety".
+    :type api_type: str
     :param name: Connection name.
+    :type name: str
     """
 
     TYPE = ConnectionType.AZURE_CONTENT_SAFETY
@@ -546,14 +572,18 @@ def api_type(self, value):
 
 
 class FormRecognizerConnection(AzureContentSafetyConnection):
-    """
-    Form Recognizer connection.
+    """Form Recognizer connection.
 
     :param api_key: The api key.
+    :type api_key: str
     :param endpoint: The api endpoint.
+    :type endpoint: str
     :param api_version: The api version, default "2023-07-31".
+    :type api_version: str
     :param api_type: The api type, default "Form Recognizer".
+    :type api_type: str
     :param name: Connection name.
+    :type name: str
     """
 
     # Note: FormRecognizer and ContentSafety are using CognitiveService type in ARM, so keys are the same.
@@ -570,10 +600,14 @@ def _get_schema_cls(cls):
 
 
 class CustomConnection(_Connection):
-    """
+    """Custom connection.
+
     :param configs: The configs kv pairs.
+    :type configs: Dict[str, str]
     :param secrets: The secrets kv pairs.
+    :type secrets: Dict[str, str]
     :param name: Connection name
+    :type name: str
     """
 
     TYPE = ConnectionType.CUSTOM
diff --git a/src/promptflow/promptflow/_sdk/entities/_run.py b/src/promptflow/promptflow/_sdk/entities/_run.py
index a3571fdb541..6094afd8945 100644
--- a/src/promptflow/promptflow/_sdk/entities/_run.py
+++ b/src/promptflow/promptflow/_sdk/entities/_run.py
@@ -45,15 +45,53 @@
 
 
 class Run(YAMLTranslatableMixin):
+    """Flow run entity.
+
+    :param flow: Path of the flow directory.
+    :type flow: Path
+    :param name: Name of the run.
+    :type name: Optional[str]
+    :param data: Input data for the run.
+    :type data: Optional[str]
+    :param variant: Variant of the run.
+    :type variant: Optional[str]
+    :param run: Parent run or run ID.
+    :type run: Optional[Union[Run, str]]
+    :param column_mapping: Column mapping for the run. Optional since it's not stored in the database.
+    :type column_mapping: Optional[dict]
+    :param display_name: Display name of the run.
+    :type display_name: Optional[str]
+    :param description: Description of the run.
+    :type description: Optional[str]
+    :param tags: Tags of the run.
+    :type tags: Optional[List[Dict[str, str]]]
+    :param created_on: Date and time the run was created.
+    :type created_on: Optional[datetime.datetime]
+    :param start_time: Date and time the run started.
+    :type start_time: Optional[datetime.datetime]
+    :param end_time: Date and time the run ended.
+    :type end_time: Optional[datetime.datetime]
+    :param status: Status of the run.
+    :type status: Optional[str]
+    :param environment_variables: Environment variables for the run.
+    :type environment_variables: Optional[Dict[str, str]]
+    :param connections: Connections for the run.
+    :type connections: Optional[Dict[str, Dict]]
+    :param properties: Properties of the run.
+    :type properties: Optional[Dict[str, Any]]
+    :param kwargs: Additional keyword arguments.
+    :type kwargs: Optional[dict]
+    """
+
     def __init__(
         self,
         flow: Path,
-        name: str = None,
+        name: Optional[str] = None,
         # input fields are optional since it's not stored in DB
-        data: str = None,
-        variant: str = None,
-        run: Union["Run", str] = None,
-        column_mapping: dict = None,
+        data: Optional[str] = None,
+        variant: Optional[str] = None,
+        run: Optional[Union["Run", str]] = None,
+        column_mapping: Optional[dict] = None,
         display_name: Optional[str] = None,
         description: Optional[str] = None,
         tags: Optional[List[Dict[str, str]]] = None,
@@ -62,26 +100,11 @@ def __init__(
         start_time: Optional[datetime.datetime] = None,
         end_time: Optional[datetime.datetime] = None,
         status: Optional[str] = None,
-        environment_variables: Dict[str, str] = None,
-        connections: Dict[str, Dict] = None,
+        environment_variables: Optional[Dict[str, str]] = None,
+        connections: Optional[Dict[str, Dict]] = None,
         properties: Optional[Dict[str, Any]] = None,
         **kwargs,
     ):
-        """Flow run.
-
-        :param name: Name of the run.
-        :type name: str
-        :param type: Type of the run, should be one of "bulk", "evaluate" or "pairwise_evaluate".
-        :type type: str
-        :param flow: Path of the flow directory.
-        :type flow: Path
-        :param display_name: Display name of the run.
-        :type display_name: str
-        :param description: Description of the run.
-        :type description: str
-        :param tags: Tags of the run.
-        :type tags: List[Dict[str, str]]
-        """
         # TODO: remove when RUN CRUD don't depend on this
         self.type = RunTypes.BATCH
         self.data = data
diff --git a/src/promptflow/promptflow/azure/_pf_client.py b/src/promptflow/promptflow/azure/_pf_client.py
index 61370d97510..a7e544cbfb4 100644
--- a/src/promptflow/promptflow/azure/_pf_client.py
+++ b/src/promptflow/promptflow/azure/_pf_client.py
@@ -86,7 +86,7 @@ def __init__(
 
     @property
     def ml_client(self):
-        """Return a client class to interact with Azure ML services."""
+        """Return a client to interact with Azure ML services."""
         return self._ml_client
 
     @classmethod
@@ -250,6 +250,7 @@ def load_as_component(
     ) -> "Component":
         """
         Load a flow as a component.
+
         :param source: Source of the flow. Should be a path to a flow dag yaml file or a flow directory.
         :type source: Union[str, PathLike, IO[AnyStr]]
         :param component_type: Type of the loaded component, support parallel only for now.
@@ -300,4 +301,5 @@ def _add_user_agent(self, kwargs) -> None:
 
     @property
     def runs(self):
+        """Return the run operation object that can manage runs."""
         return self._runs
diff --git a/src/promptflow/promptflow/azure/operations/_flow_opearations.py b/src/promptflow/promptflow/azure/operations/_flow_opearations.py
index 8d5ecd86f3f..398d5628fe2 100644
--- a/src/promptflow/promptflow/azure/operations/_flow_opearations.py
+++ b/src/promptflow/promptflow/azure/operations/_flow_opearations.py
@@ -149,6 +149,7 @@ def load_as_component(
         is_deterministic: bool = True,
         **kwargs,
     ) -> Component:
+        """Load a flow as a component."""
         rest_object = LoadFlowAsComponentRequest(
             node_variant=variant,
             inputs_mapping=columns_mapping,
diff --git a/src/promptflow/promptflow/exceptions.py b/src/promptflow/promptflow/exceptions.py
index 512667b4ec9..f7666f5c2cc 100644
--- a/src/promptflow/promptflow/exceptions.py
+++ b/src/promptflow/promptflow/exceptions.py
@@ -8,6 +8,8 @@
 
 
 class ErrorTarget(str, Enum):
+    """The target of the error, indicates which part of the system the error occurs."""
+
     EXECUTOR = "Executor"
     FLOW_EXECUTOR = "FlowExecutor"
     NODE_EXECUTOR = "NodeExecutor"
@@ -52,6 +54,7 @@ def __init__(
 
     @property
     def message(self):
+        """The error message."""
         if self._message:
             return self._message
 
@@ -62,10 +65,12 @@ def message(self):
 
     @property
     def message_format(self):
+        """The error message format."""
         return self._message_format
 
     @cached_property
     def message_parameters(self):
+        """The error message parameters."""
         if not self._kwargs:
             return {}
 
@@ -74,11 +79,12 @@ def message_parameters(self):
 
     @cached_property
     def serializable_message_parameters(self):
+        """The serializable error message parameters."""
         return {k: str(v) for k, v in self.message_parameters.items()}
 
     @property
     def target(self):
-        """Return the error target.
+        """The error target.
 
         :return: The error target.
         :rtype: ErrorTarget
@@ -87,6 +93,7 @@ def target(self):
 
     @target.setter
     def target(self, value):
+        """Set the error target."""
         self._target = value
 
     @property
@@ -155,6 +162,8 @@ def reversed_error_codes():
         return result
 
     def get_arguments_from_message_format(self, message_format):
+        """Get the arguments from the message format."""
+
         def iter_field_name():
             if not message_format:
                 return
@@ -185,4 +194,6 @@ class SystemErrorException(PromptflowException):
 
 
 class ValidationException(UserErrorException):
+    """Exception raised when validation fails."""
+
     pass