docs(AC0002): document setup-table exemption

content/docs/analyzers/ApplicationCop/AC0002.md

@@ -68,6 +68,40 @@ table 50100 "Item Category"
 }
 {{< /highlight >}}
 
+### Exception
+
+Setup tables are not reported. A setup table holds a single record, and its primary key is always blank by design. No other table relates to that record, so there is nothing for a rename or delete to cascade to.
+
+The rule recognises a setup table by convention, not by checking inbound table relations. A table counts as a setup table when either of these is true:
+
+- its only primary key field is a Code field named `Primary Key` or `PrimaryKey`;
+- it declares a parameterless `GetRecordOnce` procedure without a return value.
+
+{{< highlight al >}}
+table 50100 "My Setup"
+{
+    fields
+    {
+        field(1; "Primary Key"; Code[10]) // Not reported: setup table
+        {
+        }
+        field(2; "Default Location Code"; Code[10])
+        {
+        }
+    }
+
+    keys
+    {
+        key(PK; "Primary Key")
+        {
+            Clustered = true;
+        }
+    }
+}
+{{< /highlight >}}
+
+A single-record table that does not follow this convention is still reported. A Text `Primary Key` field is one example. A key field named `PK` or `Code` without a `GetRecordOnce` procedure is another. Set `NotBlank = false` explicitly on such a field to record that the blank key is intended.
+
 ### See also
 
 - [NotBlank Property](https://learn.microsoft.com/dynamics365/business-central/dev-itpro/developer/properties/devenv-notblank-property) on Microsoft Learn