Saves new metadata for one existing item and returns the updated item. It returns no transaction. A token id that does not exist on the drop returns 404.

On an ERC-721 SeaDrop V1 drop that is already revealed, it also regenerates the drop's metadata on IPFS and saves the new base URI to the draft; publish with POST /api/v2/drops/{slug}/publish to put it onchain. Before reveal, the change is held until POST /api/v2/drops/{slug}/metadata/ipfs runs.

On an ERC-1155 self-mint drop, the change does not reach the contract. Use PUT /api/v2/drops/{slug}/items/{token_id} instead: it makes the same change and returns the transaction that puts it onchain.