Update compat doc with acquisition restriction (#7675)

Author: jander-msft

documentation/compatibility/9.0/README.md

@@ -6,10 +6,15 @@ If you are migrating your usage to `dotnet monitor` 9.0, the following changes m
 
 | Area | Title | Introduced |
 |--|--|--|
+| Acquisition | [.NET tool installation requires .NET 9 SDK](#acquisition-net-tool-installation-requires-net-9-sdk) | Preview 1 |
 | Configuration | [`TenantId` is now required when configuring Azure Active Directory authentication](#configuration-azure-active-directory-authentication) | RC 2 |
 
 ## Details
 
+### Acquisition: .NET tool installation requires .NET 9 SDK
+
+Acquisition of the tool through `dotnet tool` command requires the use of the .NET 9 SDK as the tool requires .NET 9 run. This has no impact on what applications can be monitored nor any impact on the `dotnet/monitor` Docker image.
+
 ### Configuration: Azure Active Directory Authentication
 
 When using Azure Active Directory (Entra ID) for authentication, setting the `TenantId` option is now **required**. See [Azure Active Directory Authentication Configuration](../../configuration/azure-ad-authentication-configuration.md#configuration-options) for more details.