Is your feature request related to a problem? Please describe.
The ADK currently doesn't seem to support authentication with remote MCP servers, and also takes a long time to initialize sessions when multiple MCP servers are configured. I am using Gemini 2.5 Live. When I start a new session with an auth-based HTTPStreamable MCP server configured (e.g. https://developers.notion.com/docs/mcp), the agent simply stalls forever (no authentication-related events are emitted from run_live).

Describe the solution you'd like
A way to pre-load MCP servers for a session would be nice, making session startup time minimal which is critical for live agents. This pre-loading should also discover any necessary OAuth2 flows, allowing the client to launch any necessary links to complete OAuth flow and storing relevant tokens for when the session actually begins.