diff --git a/omagent-core/src/omagent_core/core/base.py b/omagent-core/src/omagent_core/core/base.py
index bd100e8b..32903d5a 100644
--- a/omagent-core/src/omagent_core/core/base.py
+++ b/omagent-core/src/omagent_core/core/base.py
@@ -11,51 +11,55 @@
 
 
 class STM(BaseModel):
-    class Config:
-        """Configuration for this pydantic object."""
+    """State Machine model to store temporary and contextual information."""
 
+    class Config:
         extra = "allow"
         arbitrary_types_allowed = True
 
-    image_cache: Dict = {}
-    token_usage: Dict = {}
-    former_results: Dict = {}
-    history: Dict = defaultdict(lambda: deque(maxlen=3))
+    image_cache: Dict[str, str] = Field(default_factory=dict, description="Cache for storing image data.")
+    token_usage: Dict[str, int] = Field(default_factory=dict, description="Tracks token usage per request.")
+    former_results: Dict[str, str] = Field(default_factory=dict, description="Stores results of previous requests.")
+    history: Dict[str, deque] = Field(default_factory=lambda: defaultdict(lambda: deque(maxlen=3)), 
+                                      description="Tracks limited history for each key.")
 
     def has(self, key: str) -> bool:
+        """Check if a key exists either in annotations or in extra fields."""
         return key in self.__annotations__ or key in self.model_extra
 
 
 class BotBase(BaseModel, ABC):
+    """Abstract base model for a bot instance with state management and request tracking."""
+
     name: Optional[str] = Field(default=None, validate_default=True)
-    stm_pool: ClassVar[Dict[str, STM]] = {}
-    callback: Optional[BaseCallback] = DefaultCallback()
+    stm_pool: Dict[str, STM] = {}  # Consider making this an instance attribute if shared state is not desired.
+    callback: Optional[BaseCallback] = Field(default_factory=DefaultCallback, description="Callback handler instance.")
 
     class Config:
-        """Configuration for this pydantic object."""
-
         arbitrary_types_allowed = True
 
     @field_validator("name", mode="before")
-    @classmethod
-    def get_type(cls, name) -> str:
-        if not name:
-            return cls.__name__
-        else:
-            return name
+    @staticmethod
+    def get_type(name: Optional[str]) -> str:
+        """Return the name of the instance or the class name if not specified."""
+        return name or "BotBase"
 
     @property
     def request_id(self) -> str:
+        """Retrieve the current request ID from context."""
         return REQUEST_ID.get()
 
     @property
     def stm(self) -> STM:
+        """Retrieve or initialize STM instance for the current request."""
         if self.request_id not in self.stm_pool:
             self.stm_pool[self.request_id] = STM()
         return self.stm_pool[self.request_id]
 
     def set_request_id(self, request_id: str) -> None:
+        """Set the request ID in the context."""
         REQUEST_ID.set(request_id)
 
     def free_stm(self) -> None:
+        """Release the STM instance for the current request ID."""
         self.stm_pool.pop(self.request_id, None)