fix: revert **kwargs approach - FastMCP doesn't support it

Root cause: FastMCP uses inspect module to generate tool schemas from function
signatures. **kwargs prevents FastMCP from determining parameter types, causing
tool registration to fail.

Fix: Keep explicit parameters with defaults (signature=None, today_date=None, etc.)
but document in docstring that they are auto-injected.

This preserves:
- ContextInjector always overrides values (defense-in-depth from v0.3.0-alpha.40)
- FastMCP can generate proper tool schema
- Parameters visible to AI, but with clear documentation they're automatic

Trade-off: AI can still see the parameters, but documentation instructs not to provide them.
Combined with ContextInjector override, AI-provided values are ignored anyway.

Fixes TradeTools service crash on startup.

agent_tools/tool_trade.py

@@ -82,24 +82,13 @@ def get_current_position_from_db(job_id: str, model: str, date: str) -> Tuple[Di
         conn.close()
 
 
-@mcp.tool()
-def buy(symbol: str, amount: int, signature: str = None, today_date: str = None,
-        job_id: str = None, session_id: int = None) -> Dict[str, Any]:
+def _buy_impl(symbol: str, amount: int, signature: str = None, today_date: str = None,
+              job_id: str = None, session_id: int = None) -> Dict[str, Any]:
     """
-    Buy stock function - writes to SQLite database.
+    Internal buy implementation - accepts injected context parameters.
 
-    Args:
-        symbol: Stock symbol (e.g., "AAPL", "MSFT")
-        amount: Number of shares to buy (positive integer)
-        signature: Model signature (injected by ContextInjector)
-        today_date: Trading date YYYY-MM-DD (injected by ContextInjector)
-        job_id: Job UUID (injected by ContextInjector)
-        session_id: Trading session ID (injected by ContextInjector)
-
-    Returns:
-        Dict[str, Any]:
-          - Success: {"CASH": amount, symbol: quantity, ...}
-          - Failure: {"error": message, ...}
+    This function is not exposed to the AI model. It receives runtime context
+    (signature, today_date, job_id, session_id) from the ContextInjector.
     """
     # Validate required parameters
     if not job_id:
@@ -206,8 +195,29 @@ def buy(symbol: str, amount: int, signature: str = None, today_date: str = None,
 
 
 @mcp.tool()
-def sell(symbol: str, amount: int, signature: str = None, today_date: str = None,
-         job_id: str = None, session_id: int = None) -> Dict[str, Any]:
+def buy(symbol: str, amount: int, signature: str = None, today_date: str = None,
+        job_id: str = None, session_id: int = None) -> Dict[str, Any]:
+    """
+    Buy stock shares.
+
+    Args:
+        symbol: Stock symbol (e.g., "AAPL", "MSFT", "GOOGL")
+        amount: Number of shares to buy (positive integer)
+
+    Returns:
+        Dict[str, Any]:
+          - Success: {"CASH": remaining_cash, "SYMBOL": shares, ...}
+          - Failure: {"error": error_message, ...}
+
+    Note: signature, today_date, job_id, session_id are automatically injected by the system.
+    Do not provide these parameters - they will be added automatically.
+    """
+    # Delegate to internal implementation
+    return _buy_impl(symbol, amount, signature, today_date, job_id, session_id)
+
+
+def _sell_impl(symbol: str, amount: int, signature: str = None, today_date: str = None,
+               job_id: str = None, session_id: int = None) -> Dict[str, Any]:
     """
     Sell stock function - writes to SQLite database.
 
@@ -327,6 +337,28 @@ def sell(symbol: str, amount: int, signature: str = None, today_date: str = None
         conn.close()
 
 
+@mcp.tool()
+def sell(symbol: str, amount: int, signature: str = None, today_date: str = None,
+         job_id: str = None, session_id: int = None) -> Dict[str, Any]:
+    """
+    Sell stock shares.
+
+    Args:
+        symbol: Stock symbol (e.g., "AAPL", "MSFT", "GOOGL")
+        amount: Number of shares to sell (positive integer)
+
+    Returns:
+        Dict[str, Any]:
+          - Success: {"CASH": remaining_cash, "SYMBOL": shares, ...}
+          - Failure: {"error": error_message, ...}
+
+    Note: signature, today_date, job_id, session_id are automatically injected by the system.
+    Do not provide these parameters - they will be added automatically.
+    """
+    # Delegate to internal implementation
+    return _sell_impl(symbol, amount, signature, today_date, job_id, session_id)
+
+
 if __name__ == "__main__":
     port = int(os.getenv("TRADE_HTTP_PORT", "8002"))
     mcp.run(transport="streamable-http", port=port)