Ever since writing [[P1240R0] (Scalable Reflection in C++)](https://wg21.link/p1240r0), but more so since [[P2996R0] (Reflection for C++26)](https://wg21.link/p2996r0), we have been requested to add a capability to annotate declarations in a way that reflection can observe. For example, Jeremy Ong presented compelling arguments in a post to the [SG7 reflector](https://lists.isocpp.org/sg7/2023/10/0450.php). Corentin Jabot also noticed the need while P1240 was evolving and wrote [[P1887R0] (Typesafe Reflection on attributes)](https://wg21.link/p1887r0), which proposes syntax not entirely unlike what we present here.