Python: [Python] `MCPStreamableHTTPTool` drops per-argument `description` fields when loading tools from an MCP Server

[hjerbii]

Hello 😊

When using MCPStreamableHTTPTool and after loading tools using load_tools() (from _mcp.py), it builds Pydantic models for MCP tools’ inputs but omits per-argument description.

The root cause seems to be _get_input_model_from_mcp_tool, which maps only type (and required/default) and discards description:

[giles17]

Closing because this issue has been solved in this PR: #2382