Will my customers see how much luggage is included before they pick a flight on my portal?

Yes, in most cases they will see the baggage allowance next to each fare before they choose, but how much detail appears depends on the airline and on which supplier the fare came from.

When a flight booking API returns a fare, it normally sends the cabin bag and checked bag allowance for each passenger along with it, and the portal shows that on the results page and again on the review page before payment. For most full service airlines this comes through clearly, either as a number of bags or as a weight limit per person, so your customer can compare a cheaper fare that carries nothing in the hold against a slightly higher one that includes a suitcase. Where it gets thinner is with low cost carriers and the very cheapest branded economy fares, because some suppliers send only the basic fare with no baggage detail attached, and the true allowance is confirmed only when a bag is added as a paid extra during booking.

We can only display what the supplier gives us, so if a particular airline or content source leaves that field empty, the portal shows that baggage is not included rather than inventing an allowance. Whether your customers can also buy extra bags at the time of booking depends on the supplier supporting paid extras on that route, and not all of them do.

The practical step is to run a few searches on the routes you sell most, look at what the baggage line says for both a full service and a budget carrier, and tell us which supplier you are using if anything looks blank or wrong so we can check how that content is coming through.