Custom field values keyed by their administrator-defined identifiers. Omitted identifiers remain unchanged, and a null value clears the corresponding custom field. The accepted type for each identifier is defined by the tenant's custom field configuration. Boolean values are JSON booleans; Text and Long text values are strings; Email values are email-formatted strings; URL values are HTTP or HTTPS URL strings; Number values use canonical base-10 decimal strings from -99999999999999.999999 through 99999999999999.999999 with up to six fractional digits and no insignificant trailing fractional zeroes; Date values are ISO 8601 YYYY-MM-DD strings; Date-time values are ISO 8601 timestamps with a UTC offset; and JSON values may use any JSON-serializable value. Decimal strings are the precision-safe Number request representation. JSON numeric inputs remain accepted for compatibility, but their precision may depend on the client's number handling.