Contract Bridge and the short club convention
As Alexander Woo says in a comment, there is no &quot;short club convention&quot; - at least, no single one.  Frankly, there is no &quot;X convention&quot; for any X - you will find people who play X a different way than you, and will insist theirs is the right way (or even the only way).  The correct answer to your question is &quot;what have you and your partner agreed to?&quot; and &quot;how are your responses tuned to fit that agreement?&quot;  It is always a risk to say &quot;we play X&quot; and assume partner plays it the same as you do.
&quot;Short Club&quot; systems common enough for me to think of immediately include:

The most common &quot;short club&quot; played by thousands of (usually weaker) players at home and in tournaments: &quot;5-card majors, 4-card diamonds, 3 cards clubs, with 4=4=3=2 opened 1 club instead of 1 diamond&quot; (= is a writing convention meaning &quot;suits in order&quot;, so 4=4=3=2 is 4 in both majors, 3 diamonds, 2 clubs).  Perfectly playable, as long as it doesn't evolve into &quot;I couldn't raise on 5, what if you only had two!&quot; or other monstrous convolutions to care for this very rare (3% in a strong NT) hand type.  In this case, no, 1 diamond does not promise 5 (1D is opened on 3=3=4=3, for example).

A very common system in my area is &quot;Montréal Relay&quot;, where 1 diamond does promise 5, 1 club is frequently 2 (the key of this system is that the &quot;relay&quot;, 1C-1D is catchall, and only &quot;denies a 5-card major&quot; (and a few other rare hands)).  Now the issue is what to do with 4=4=4=1; some put it into 1C, some into 1D, some play some sort of 2D 4441 bid,...
I am amused by the fact that there are more players of Montréal Relay where I live out West, than there are in Montréal itself.

Becoming more common in the ACBL (due to convention liberalization), and very common elsewhere, is 1 club &quot;clubs or balanced&quot;, usually with transfer responses (so 1C-1D shows 4+ hearts, 1C-1H shows 4+ spades,...)  Here, 1D is almost always unbalanced, almost always 5 (could be 4=4=4=1, many play not 3=3=5=2 or (32)=5=3).

Then there are all the two-way and three-way club systems like Swedish (&quot;weak NT or strong hand&quot;) and Polish (&quot;weak NT or 15-19 clubs or strong hand&quot;) Clubs. The rules for those vary a lot as well, but we're leaving the world of what would be called a &quot;short club&quot; convention.


Of course, there's the really old-fashioned &quot;short club&quot;, where as well as the clubs hands, you open 1 club with a hand not quite strong enough to open a strong 2.  1C is &quot;not forcing&quot;, but partner knows not to pass it, &quot;just in case&quot;.
This system works much better with the similarly old-fashioned spoken bidding clues, where, as Ron Andersen (prolific bridge author, teacher and expert player) said about his &quot;mother's bridge club&quot; (quoting from memory):

If a player has 13 or so with real clubs, she opens &quot;one club&quot;.  If it's 3 poor (or 2) clubs, she opens &quot;a club&quot;.  If she has a strong hand that shouldn't be passed, it's &quot;I'll start with a club&quot;.

In case it wasn't obvious, this &quot;help&quot; is highly unethical if done by habit, and cheating if on purpose.  Don't.