I see a lot of online descriptions of calories in beef, but none of these say whether the beef is uncooked or cooked. Should I assume they are talking about raw, uncooked beef, or is it just random useless information about which I can make no assumptions?
If they really don't tell you whether it is for cooked or uncooked, then you indeed can't know it.
I would be rather surprised at finding such unlabeled data though. It is rare, and if you, for some reason, happen to find a site so bad that it doesn't define what it measures, then just use a different site. For example, the site you linked lets you pick which calories you want to see, and with the link you gave, it is for cooked beef. You can switch to uncooked, if you wish (and to a weight measurement, which makes it more comparable).
Also, beef is a natural product, not an engineered food with a standardized manufacturing process. The numbers presented on nutrition labels are an average created after multiple measurements of the same food. The difference between two different batches of beef can easily be larger than the difference between the number published for cooked and uncooked beef.