One of the rules we all learned in kindergarten was to tell the truth. As we get older it may feel more complicated, especially in relationship to small beings. We want to protect them, help them thrive, do what is best for them and sometimes that leads to a plan of not telling them the truth.
For example, if your small being is a picky eater, have you ever tried to sneak really small pieces of vegetables into Mac and cheese? I know several small beings who now carefully inspect their food before eating it due to this tactic. They learned asking what was in the food would not lead to the truth. Instead they search the food and if anything seems suspicious, won't eat.
The best way to protect your small being is by teaching them they can always believe you! Even if it is not what they want to hear. Yes, there are tiny pieces of carrot in your Mac and cheese and it is still yummy. (Including no there is not another food option helps if feeding is challenging for your small being).
Simplification may be needed, depending on the age of your small being. They do not need all the details and explanations. What they need is clear and simple honesty.
Personally, I have been asked many times, how to describe to a small being who I am or why they are seeing me. My answer is simple: I am a teacher who teaches people how to behave better. Then ask if there are behaviors that might need help. Behaviors of this small being and the big being can be discussed in neutral and direct way. It is a clear and honest answer. It allows the small being to be an active participant in the change and understand what is happening.
If we expect our small beings to tell us the truth (which we do), we need to tell then the truth! Honesty, simple and clear, is the best policy!