uniqueIdentifier — your item's unique key in the Fairly Made system. It defines the granularity of analysis you want Fairly Made to perform: one uniqueIdentifier = one analysis. Format: resource prefix (SUP, MAT, COMP, PACK, MP, PI, FILE, BP) followed by your own segments separated by underscores (_). See the API introduction for details.
Id vs unique identifier — when a field has both a UUID (*Id) and a client reference (*UniqueIdentifier), send exactly one, not both and not neither.
Owner (supplier) — on manufactured materials, components, and products: send ownerId or ownerUniqueIdentifier (with ownerKind = SUPPLIER), or an address — not both owner and address.
One item = one supplier — a created item (manufactured material, component, manufactured product, or packaging) maps to one supplier and the traceability steps tied to that supplier. If what you consider a single item involves multiple suppliers, create separate items — one per supplier.