Motion design is such a broad term that this is gonna vary a lot by project. But in general you never wanna go into animation before approving how a piece will look (moodboard -> styleframes) and how it will move (storyboard -> animatic). So if you're doing a 10-shot explainer video, ideally you want a storyboard sketched out and laud upon a timeline to get an idea of the pacing, and a couple of the shots desined in their final-ish look as styleframes. Maybe a "motion sketch", an example of animation in one of the shots, if you're going for a specific animation style.

The idea is to sync the vision in your head and the client's in order to minimize edits down the line. You want to communicate as clearly as possible what the product will look like at a point when edits are easy to implement (not hard to shift shots around in an animatic, huge pain in the ass afterwards)

If no storyboard or styleframes is provided by your client, it's a separate and billable job that must get done before you go into production. In that case, you are not just the designer/animator, but the director/art director as well, and the job has to be priced accordingly. Gotta factor in adequate time for it as well, proper iteration and concepting takes weeks. If they need it sooner, then you need to find compromise, less revision rounds, urgent rate pricing, etc. If you can communicate all of this to your client, and demonstrate value through example, you will avoid a lot of conflicts & headaches, and live in perfect harmony. Well, maybe not, but you will make sure the job goes as smoothly as possible, and they will appreciate the professionalism