Filter ID tags by standard properties or administrator-defined custom fields. Send a scalar under a literal dotted key, for example filter[customFields.fleetLabel]=North. Text, email and URL fields match substrings; boolean fields accept true, false, 1 or 0.

For number, date and date-time fields, send inclusive bounds under the dotted key, for example filter[customFields.fleetNumber][from]=10&filter[customFields.fleetNumber][to]=20. Either bound may be omitted. Multiple criteria combine with AND. Unfilled criteria are ignored. Non-empty unknown, inaccessible, disabled or unfilterable custom-field keys return 400; malformed values for usable fields return 422. Operator-scoped fields match only ID tags whose current operator is assigned to the field. Custom-field filters are applied before pagination. URL-encode query keys and values when sending the request.