A call to action, or CTA, is the specific instruction a piece of content gives a viewer at the moment it wants them to act — follow, visit a link, book a call, buy. It is a single ask, placed where attention is highest.
A video with two calls to action usually gets neither: the ask has to be the one thing the viewer is left with.
A scenario's shot list names the call to action for the same reason: deciding it before filming, rather than bolting one onto the caption afterward, is what keeps it matched to the video.
The strongest call to action is usually the simplest one available for that specific video, rather than the one an account defaults to on every post — a video that just answered a question earns a different ask than one that just entertained.
A common mistake is choosing the call to action after the video is edited, from a short list of defaults, rather than deciding it before filming — the two produce different videos, because a video built to earn a follow is paced and shot differently from one built to earn a link click.
A weak call to action is often not the wrong ask but the right ask placed wrong: buried in a caption nobody reads to the end, or spoken once in the middle of the video rather than near the end, once the video has actually earned the viewer's attention.
Where it comes from
Meta's own Ads Manager documents this directly, offering advertisers a fixed set of call-to-action buttons — Learn More, Shop Now, Sign Up, Download among them — chosen to match the campaign's own objective, so the ask fits what the ad is actually for.
Read the source: Meta Business Help Center — Available Call-to-Action Buttons in Ads Manager.
What Rankfield reads
The landing page answers this directly, in its own words:
Your account end to end, your competitors, and the wider market around you: posts, videos, captions, comments, rhythm, what you offer. It watches the videos, not just the numbers under them.