Provably-Fair Multi-Winner Picker

Choose this endpoint when you need to select multiple distinct winners (N > 1) from a list and require cryptographic verifiability — i.e., anyone can re-run the selection and confirm it matches using the same seed and nonce. Prefer the sibling single-winner endpoint when you only need one pick. Use this over a simple random shuffle when auditability and fairness proof matter, such as public contests, lotteries, or regulated draws.

• count exceeds number of candidates — cannot pick more winners than there are entries
• missing required parameters (candidates, count, round, client_seed, nonce) — HTTP 400 bad request
• candidates list is empty — returns error or empty result
• duplicate candidates in input may affect distinctness guarantees
• network timeout or server unavailability — HTTP 5xx