Middleware tools list (different tool set based on user access)

Is your feature request related to a problem? Please describe.
Cannot implement dynamic list of tools per user. My MCP will support many users at the same time. Each user has a different tool set based on his current project.

Describe the solution you'd like
Incapsulated middleware tools list management. The list of tools could be loaded based on custom list of tools of a user from my custom database and applied into csharp-sdk api to expose it to MCP client as usual for the connection.

Additional context
The MCP server by default has no tools. Just after user got connected Unity Engine via SignalR using token, the list of tools dynamically got fetched from Unity Engine. Then user may use an MCP client to connect to the MCP server with the access token and start using the tools. User may even create brand new custom tool inside of the Unity Engine and the tool will be uploaded to the MCP server into private tools list.

The issue names the csharp-sdk API, middleware tool-list management, and the MCP connection flow, but no files or tests. Start by locating the API and middleware surfaces for registering tools, then define how a user's custom tool list is loaded and applied after access-token authentication. Done means different users can receive their own tool lists and MCP clients see those tools for the connection.