diff --git a/server.py b/server.py
index 0f7d15a..b595b3d 100644
--- a/server.py
+++ b/server.py
@@ -14,6 +14,21 @@ import schwab_scraper.unified_api as api
 # Initialize FastMCP
 mcp = FastMCP("SchwabScraper")
 
+def serialize(obj: Any) -> str:
+    """Safely serialize Pydantic models or datclasses to JSON string."""
+    if hasattr(obj, "model_dump_json"):
+        return obj.model_dump_json()
+    elif hasattr(obj, "model_dump"):
+        return json.dumps(obj.model_dump(), default=str)
+    elif isinstance(obj, list):
+        # Handle lists of models
+        return json.dumps([
+            o.model_dump() if hasattr(o, "model_dump") else o 
+            for o in obj
+        ], default=str)
+    return json.dumps(obj, default=str)
+
+
 @mcp.tool()
 async def get_session_status(debug: bool = False) -> str:
     """Get the current session status of the Schwab scraper.
@@ -22,7 +37,7 @@ async def get_session_status(debug: bool = False) -> str:
         debug: Enable debug logging
     """
     result = await api.get_session_status(debug=debug)
-    return json.dumps(result)
+    return serialize(result)
 
 @mcp.tool()
 async def list_accounts(debug: bool = False) -> str:
@@ -32,7 +47,7 @@ async def list_accounts(debug: bool = False) -> str:
         debug: Enable debug logging
     """
     result = await api.list_accounts(debug=debug)
-    return json.dumps(result)
+    return serialize(result)
 
 @mcp.tool()
 async def get_account_overview(account: Optional[str] = None, debug: bool = False) -> str:
@@ -43,7 +58,7 @@ async def get_account_overview(account: Optional[str] = None, debug: bool = Fals
         debug: Enable debug logging
     """
     result = await api.get_account_overview(account=account, debug=debug)
-    return json.dumps(result)
+    return serialize(result)
 
 @mcp.tool()
 async def get_positions(account: Optional[str] = None, include_non_equity: bool = False, debug: bool = False) -> str:
@@ -55,7 +70,7 @@ async def get_positions(account: Optional[str] = None, include_non_equity: bool
         debug: Enable debug logging
     """
     result = await api.get_positions(account=account, include_non_equity=include_non_equity, debug=debug)
-    return json.dumps(result)
+    return serialize(result)
 
 @mcp.tool()
 async def get_transactions(
@@ -81,7 +96,7 @@ async def get_transactions(
         time_period=time_period,
         debug=debug
     )
-    return json.dumps(result)
+    return serialize(result)
 
 @mcp.tool()
 async def get_morningstar_data(ticker: str, debug: bool = False) -> str:
@@ -92,7 +107,7 @@ async def get_morningstar_data(ticker: str, debug: bool = False) -> str:
         debug: Enable debug logging
     """
     result = await api.get_morningstar_data(ticker, debug=debug)
-    return json.dumps(result)
+    return serialize(result)
 
 @mcp.tool()
 async def upload_cookies(cookies_json: str) -> str: