Necroing this after 8 years because it's still a good idea. I was going to make my own post explaining why but I'll just do it here.
Take this example. Adding "Cholaxium" (a metal I just now made up) to the game tells players nothing of its properties for example, and there's no way to convey it easily in game unless you have a reaction with a description that uses it, and even then it means the player would need to know to find that reaction (its own description limited to a certain number of characters) to find the description which explains what Cholaxium is and how to use it, rather than simply clicking on Cholaxium to read the description itself, a far easier alternative given the player may well be more likely to encounter the material before stumbling upon the reaction that uses it, if the civ they play even has that reaction. The same could be said for any item for example. What is a Jornian puzzle box? Why is it different than a normal one? What about a weapon just called a swayyal? How do you know what that is? And what if that swayyal is made from cholaxium? It just becomes gibberish with no way to easily parse it in-game.
Essentially anything outside mythology/history (embedded in the public consciousness, you could add orchichalum or a katana to the game and most people would know what you are talking about or find out with little effort) or descriptive names (hard gray metal, soft yellow metal, axe-bayoneted compound crossbow, etc) suffer from this issue, and so you're either limited to cribbing from the ancients or utilizing a clunky, long-winded descriptive naming schema that either jarringly stands out from the rest of the game (an inventory of "gold, silver, and gleaming purple metal") or mandates overhauling all other content to make it match tonally, the alternative being peppering your mod with custom nomenclature and then demanding the player flit between the game and tabs of your mod's wiki (if you even made one) to know what it is they are looking at and what to do with it.
And yes, with graphics you do gain the advantage of a visual aid, but details like texture, scent, taste, utility, special attacks, or historical significance among other things can't easily be gleaned from a pixel sprite, but can be explained in a description. This change could allow a large portion of time spent out-of-game to be negated, allowing the player to learn from and experience the mechanics and lore of the mod within the game itself rather than scrolling through explanatory text on the forum or steam page or wherever.
That said, I understand this could get complicated. Nested descriptions, such as a means to select a cholaxium swayyal and be able to navigate to the description for a swayyal and cholaxium within the same item, would be more work than merely adding making the DESCRIPTION: token available to a broader range of things, so I would say the loss of that wouldn't be too significant if it stood in the way of implementing this feature.
In addition I don't think the currently extant vanilla stuff needs to be given descriptions should this be implemented, given most of it is easily understandable stuff found in the real world like historical weapons and armor, or real-world plants and minerals, but if that is what would be required to make this happen I would personally comb through all the raws on behalf of the development team and add descriptions to everything that needed them, something I am capable of and very willing to do.
In short, expanding the utility of the description token would be a massive boon for the creative efforts of the modding community with minimal effort.