I have been under the impression that the improvement has an area effect. (I fondly recall the days when there were tiny little freighters running around the map and commercial starbases with area effect.) The wiki description is of an improvement that does nothing unless the planet is an end point in a trade route. Is that true?
Also, I don't see the effect of Trade Capital in the Civilization.Trade list. Is it and Trade Post supposed to show up discretely? or are they wrapped up in the endpoint values?