If you're building MCP servers in .NET with instance-based tool classes — the kind that take ILogger<T> , HttpClient , or a repository through constructor injection — there's a good chance you've already hit this at runtime: System.Reflection.TargetException: Non-static method requires a target. No warning at startup. No compile-time error. Just a crash the moment an AI model calls your tool in production. This post explains why it happens, shows the two-line fix in ...