Access to HttpContext within handler delegates like ListToolsHandler for authentication-aware logic

Is your feature request related to a problem? Please describe.
I'm currently working with the Model Context Protocol in .NET and would like to dynamically filter the tools returned by the ListToolsHandler based on the current user's authentication context. However, it doesn't seem possible to access the current HTTP context inside the ListToolsHandler or similar delegate handlers. This limits the ability to tailor tool availability based on user identity or permissions.

Describe the solution you'd like
I would like to be able to access the current HttpContext (or any equivalent user context) from within handlers like ListToolsHandler, CallToolHandler, etc. This would allow implementing features like per-user tool availability or custom authorization logic.

Describe alternatives you've considered
I haven't found a clear alternative to accessing the HTTP context directly from these handlers. Most approaches seem like workarounds and don't offer a clean or reliable way to integrate authentication data.

Beginne damit, nachzuverfolgen, wie ListToolsHandler und CallToolHandler im C# SDK aufgerufen werden und wo der aktuelle Request-Kontext verfügbar ist. Vergleiche den angeforderten HttpContext oder einen gleichwertigen Benutzerkontext mit der bestehenden Handler-API. Die Umsetzung sollte eine dokumentierte, zuverlässige Möglichkeit schaffen, mit der Handler eine benutzerspezifische Authentifizierungs- oder Autorisierungslogik anwenden können.