The MS I'm querying recently placed in a reputable writing contest. Hooray! Obviously this is news that goes in all future query letters. (In the same paragraph with the other "meta data" like word count and title, yes?)
1) What's the best way to phrase this in a query? I didn't win, but I was runner-up. Other contests don't rank anyone beyond the winner (a la the Oscars), so would that just be 'I finaled'?
2) Are there contests big enough that you should send an update to agents with partials or fulls? My instinct tells me something like a Golden Heart or Thriller (national, big awards ceremony, etc.) is major news, but few others are. And that mentioning in a well-timed nudge is one thing, while sending a random update out of the blue is quite another.
(1) "Title was the runner up in the 2017 Idol Hands Are the Devil's Playground Writing contest (sponsored by the Beel, Zee and Bub writing conference.)"
(2) It won't kill you to include this in a well-timed nudge. It won't kill you if you send a random update out of the blue either. I'd prefer the former to the latter only because I will reply to a nudge but not an update.
Bottom line: I'm delighted your novel won this accolade but it makes zero difference to me. (Sorry.)
Here's why: your competition is from too small a pool, and most likely only unpublished manuscripts. You'd have to actually win one of those contests to have the same odds as getting a request for a full from an agent.
Here's the math:
Most of those contests have fewer than 100 entries. I have five hundred queries in a month (6000 a year) and even when I'm on a full-requesting spree as I am now, I've asked for only 60 manuscripts.
requested full 1:100 (sixty out of six thousand)
win a contest: 1:100
When you add win, place or show:
Final in a contest: 3:100
(requested fulls still 1:100)
What this means for you: it certainly won't hurt to mention this, and doing well in a contest is terrific reassurance that you're not writing dreck, but it won't help you in the incoming queries enough to spend lots of time or money entering these. Winning a contest will get my attention probably. What keeps my attention is your novel.