CSV, XLSX or JSON, one company per row. Columns are matched to lead fields by name (you can change each match). A row needs at least a company name. Re-uploading the same table updates rows instead of duplicating them, and never blanks fields people filled in.

Describe a different topic or segment. Claude searches the web and proposes companies. Every row must cite a page that the search actually returned; rows without one are dropped. Nothing is saved until you select rows and add them.