SQL70558: The column definition from this OPENQUERY function cannot be verified, and the operations involved with it might not be understood correctly.
Depending on how your project and build is configured, this warning it may or may not fail the build. Regardless, if you have to use OPENQUERY and don't want the warning, you can use the Suppress TSql Warnings property on the stored procedure. To view this property in Visual Studio, click on the .sql file in the Solution Explorer window. You should now see this property in the last row of the Properties window. Enter the 70558 warning number. The warning should now be suppressed and will no longer appear in the Error window or the build output.
The Suppress TSql Warnings property can be used to suppress other warnings as well. To suppress multiple warnings just delimit them with a comma.