The NFC attendance solution is an Edusign add-on installed and configured by the Edusign team. Atomically partially update up to 100 NFC tags belonging to the authenticated school. This operation updates existing NFC tags only; it never creates tags. Use the unique row IDs returned by GET /nfc; tag numbers are not unique. IDs must be unique within the request. A classroom must already exist in the school. Names are matched without regard to case or accents and saved with their stored spelling. Multiple matching stored spellings are rejected; an administrator must remove the duplicate classroom names. Omitted fields remain unchanged; set classroom to null to clear it. Unsupported properties are ignored; maxDistanceMeters and tagNumber are read-only. Each item without any writable field is rejected. If any NFC tag or classroom is unavailable to the school, or any stored configuration needed by the request is malformed, no NFC tag is changed. Each result lists only values that actually changed; updatedCount is the number of processed NFC tags, including no-ops. Signing windows use boundaries relative to the course start and end. One boundary in each array defines one course-wide access interval, including when both margins are zero. Two boundaries in each array define separate access intervals around the course start and course end. Both arrays must have the same length. Boundaries are exclusive. A pair of zero-minute boundaries disables that interval; updates must leave at least one interval enabled.