Distinguish Main Lines from Alternates in API Response

I want a field or flag in the API response (specifically v3) to reliably distinguish the 'main line' from 'alternate lines' for markets like Spreads and Totals. Currently, they are bundled in the same array without identifiers, and heuristics like vig scoring, median, first entry, or sticky fail in various scenarios. This is critical for reliably picking the main line.