Seems fairly straightforward, see the NPC Race features table in the DMG, page 282. It gives the details for 25 races, from the PHB and MM, giving the ability mods and features to add to the NPC Templette. So, if Gnolls are on the table, all it would need is the ability mods and a reference to the MM stats (or a monster stat block from Chapter One, maybe) for the racial traits: no details on Gnollish names or culture, just bare numbers for somebody to use in a tabular format. You can really already do that for Gnolls from that DMG table, frankly, so I think it is a solid model of what we can expect (much longer, maybe, but probably not more info; notably, the NPC PHB races have different NPC mods, so who knows).
You can't just list features without an explaination of what they do, how could anyone use that? Plus you need stuff like known lauguages, size, speed, age, weight, ect...
At the very least you'd need a table explaining what particular features do!
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