Function
The course's own description, from the content manifest
The leading clause, trimmed; the whole trimmed description if it has no cut point
A sharing card's headline is the one line a reader sees before deciding
whether to click — and on X it is now the only thing they see, since the
card renders image-only in the feed. A catalog name spends that line badly:
Basic Course names a row in a database and tells a reader nothing about
what they would learn. American pronunciation from the ground up tells them
exactly.
Course descriptions in this catalog are already written that way — a promise, then a colon, then the specifics. So the headline is the part before the colon, or before the first sentence end when there is no colon.
The fallbacks matter more than the happy path: a description with neither punctuation mark, or one that opens with the mark, must still yield a headline. An empty card headline is worse than a long one.
The promise a course makes, extracted from its description.