Need help checking a key

Try ASF, it'll tell you what game it is for but if you don't own the item it will activate the key on your account.

Haven't all those Raise games been free at one point (and should be considered free?) :x
Since you said mass giveaway, sure as hell this one.

Games from massive giveaways don't give reduced CV; they give none at all. Making giveaways for keys you got from giveaways, especially if they were from fishy sources (steam groups that beg devs for keys for example) is risky and I would not suggest it.

That being said there is no tool to check what the key is for. The only way would be to find someone who owns the game and have him try to activate, if it is for that game the steam will give him a message saying he already owns it.

I created 2 giveaways that day for "Raise" games, both received from mass giveaways (from sites, not steam groups), Occult, which is marked as no CV, which was marked as received by the winner, and one for Arcane, which is currently marked as reduced CV. I created them mostly to try to keep up my win/giveaway ratio since I won a bunch of games (like 5) within a couple of days since I don´t go around buying bundles to give keys away (I can´t afford it).
I thought there was at least a tool that allowed you to check whether a key was activated, and the account it was activated under.