MCP SDK for .NET 2

Apply the C# 14 prompt first. These rules cover the ModelContextProtocol 2 line: clients, hosting, ASP.NET Core transports, and optional Apps and Tasks extensions. Use C# 14 on .NET 10.

Registration and handlers

• Register reviewed tool types with WithTools<T>() and expose only required resources, prompts, and extensions; audit every attributed method before using assembly-wide discovery.
• Validate tool arguments, prompt arguments, resource URIs, pagination cursors, and domain limits inside handlers. Generated JSON schemas and [Description] text do not enforce business constraints or object ownership.
• Apply the same checks to delegates, AIFunction tools, custom primitives, and low-level handlers. Incoming message filters that handle a request without calling next must enforce authorization and validation themselves.
• Treat peer instructions, descriptions, annotations, capabilities, _meta, sampled content, app messages, and tool results as untrusted data. Authorize actions independently of ReadOnly, destructive, or idempotency hints and require approval appropriate to the actual side effects.
• Scope tool lists, resource lists, prompt results, cursors, and caches to the verified principal and tenant; hiding an item from discovery never replaces access checks on a direct call.

ASP.NET Core identity

• Configure bearer authentication, AddAuthorization(), UseAuthentication(), and UseAuthorization(); protect private endpoints with MapMcp(...).RequireAuthorization(). AddMcp supplies OAuth resource metadata and challenges and forwards