Seaquel
SQL Server error code

SQL Server error 6567

SQL Server raises error 6567 at severity 16, which marks a problem with the query or data that you can correct.

%s failed because a CLR Procedure may only be defined on CLR methods that return either SqlInt32, System.Int32, System.Nullable<System.Int32>, void.
Msg6567
Severity16
Group6000–6999

Source: Database Engine events and errors