how transparent should quotes really be?

I was getting some work done on my car last week, and the mechanic gave me a quote that was pretty vague... like "parts and labor" without breaking down the specifics. It felt kinda sketchy, you know? I ended up going somewhere else where they listed everything clearly. Got me thinking - how detailed do you guys expect quotes to be when you're paying for services? Is it normal to ask for a full breakdown, or am I being overly cautious here?