Feat: Redesign and refactor agent module (#9113)

### What problem does this PR solve?

#9082 #6365

<u> **WARNING: it's not compatible with the older version of `Agent`
module, which means that `Agent` from older versions can not work
anymore.**</u>

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

rag/utils/mcp_tool_call_conn.py

@@ -239,7 +239,17 @@ def shutdown_all_mcp_sessions():
     logging.info("All MCPToolCallSession instances have been closed.")
 
 
-def mcp_tool_metadata_to_openai_tool(mcp_tool: Tool) -> dict[str, Any]:
+def mcp_tool_metadata_to_openai_tool(mcp_tool: Tool|dict) -> dict[str, Any]:
+    if isinstance(mcp_tool, dict):
+        return {
+            "type": "function",
+            "function": {
+                "name": mcp_tool["name"],
+                "description": mcp_tool["description"],
+                "parameters": mcp_tool["inputSchema"],
+            },
+        }
+
     return {
         "type": "function",
         "function": {