The general rule of thumb is that yes, you should provide full disclosure to your lender.
Keep in mind, the lender wants to be able to give you a mortgage, this is how they make money.
If you feel that you need to hide something, then perhaps the person or lender you are working with is not the right one for you.
Just like a trusted advisor such as a lawyer, an accountant, or a doctor, you should feel comfortable and trust the person who is helping you with your mortgage. After all, this is the largest investment / purchase of your life.