Author a new flashcard and schedule it. front is the prompt/question, back is the answer. Optional deck groups cards (default 'default'). Returns JSON {card_id, due}. The card is due immediately (first review).

List cards due for review now (due <= now), soonest first. Optionally filter by deck. Returns a JSON array of {card_id, front, back, deck, due}. Quiz the user with front, check against back, then call grade_card. Returns '[]' when nothing is due.

Record a review of a card. rating is how well it was recalled: 'again' (forgot), 'hard', 'good', or 'easy' (1-4 also accepted). FSRS updates the schedule; returns JSON {card_id, rating, next_due, reps}.

List cards (newest first) regardless of due date, for an overview. Optionally filter by deck. Returns JSON array of {card_id, front, back, deck, due, reps, suspended}.

Edit a card's content without disturbing its schedule. Update any of front, back, deck (omit or pass null to leave unchanged); the FSRS review state (difficulty, stability, due date, reps) is preserved. Use this to fix typos or add context instead of creating a duplicate card. Returns JSON {card_id, front, back, deck}.

Shelve a card: keep it (with its full history and schedule) but remove it from the due queue, so it won't surface in due_cards until unsuspended. Reversible, non-destructive alternative to delete_card for cards you're unsure about. Returns JSON {card_id, suspended}.

Un-shelve a previously suspended card, returning it to the review queue (it becomes due again per its existing schedule). Returns JSON {card_id, suspended}.

Delete a card by id (reset / cleanup).

Summary of the card box: total cards, how many are due now, total reviews, and the deck list. Optionally scope counts to one deck.