How does this work? Here’s what each of the steps do:
– The source step creates a simple table with two columns called firstname and lastname using #table (see here for more details on that).
– The tabletype step declares a new table type with two columns (the same two columns in the table from the previous step) and then adds a metadata record to this type. In that record the Documentation.FieldDescription field contains the text values that will appear as tooltips when you hover over each column.
– The replacetype step replaces the type of the table returned by source with the type declared in tabletype.
Click through for the code.