What is necessary for a table in ServiceNow to be usable in scripts?

For a table in ServiceNow to be usable in scripts, it is essential that it be defined in the system dictionary. The system dictionary contains the metadata that describes all the tables and fields within the ServiceNow platform. This metadata is required for scripts to reference the table correctly, ensuring that the system understands the structure and type of data within that table.

When a table is defined in the system dictionary, it becomes part of the overall data model that ServiceNow uses during scripting, allowing developers to access, manipulate, and interact with the data effectively. This definition includes information about the table's properties, such as its columns, data types, and relationships with other tables.

Other options, like needing to be a custom table or having active business rules, do not directly impact a table's usability in scripts. While extensibility can add functionality to the table, it is not a prerequisite for scripts to functionally interact with the table. Therefore, being defined in the system dictionary is the key requirement for a table to be referenced and utilized within scripts in ServiceNow.