> ## Documentation Index > Fetch the complete documentation index at: https://docs.closient.com/llms.txt > Use this file to discover all available pages before exploring further. # Verify a serialized unit for returns > Decide whether a scanned GTIN + serial was sold by the authenticated organization, when, under which transaction, and whether it has already been returned. Intended for a return desk scanner or POS plugin: one call, one decision object. Decisions are computed **only** from the querying organization's own EPCIS events — another retailer's sale of the same GTIN + serial is never visible here, and a unit this organization has no events for is reported as ``unknown_serial`` rather than falling back to anyone else's history. Recall status is the one deliberate exception: it is public product-safety information, so an open recall covering the unit is reported regardless of which organization published it. The lifecycle states ride GS1 CBV 2.0 dispositions — ``retail_sold`` for a sale (bizStep ``retail_selling``) and ``returned`` for a return (bizStep ``returning``). Caller must hold an OWNER or MANAGER membership on the organization. ## OpenAPI ````yaml /openapi/openapi-epcis.json get /epcis/api/2.0/verification/serial openapi: 3.1.0 info: title: EPCIS 2.0 API version: 2.0.0 description: > GS1-conformant EPCIS 2.0 event capture and query API. ## Authentication All endpoints require an API key passed via the `X-API-Key` HTTP header, unless otherwise noted. ``` X-API-Key: csb__ ``` Generate API keys in **Settings > API Keys** in your dashboard, or via the Account API. Session-based (cookie) authentication is also accepted for browser-based access. ## Rate Limits | Tier | Requests / minute | Requests / day | |-------------|-------------------|----------------| | Default | 300 | 10,000 | | Custom | Contact us | Contact us | Rate-limit headers are included on every response so callers can self-throttle without hitting our 429s ("informed governor"): - `RateLimit-Policy` — every active window, e.g. `300;w=60, 10000;w=86400` - `RateLimit-Limit` — quota for the **most-restrictive** currently-active window - `RateLimit-Remaining` — requests left in that window - `RateLimit-Reset` — seconds until that window resets (relative; clock-skew safe) Legacy `X-RateLimit-*` aliases are also emitted for back-compat. `X-RateLimit-Reset` keeps the absolute Unix-timestamp shape to avoid breaking existing consumers. When rate-limited, you receive `429 Too Many Requests` with a `retry_after_seconds` field in the error envelope and a `Retry-After` header. ## Pagination List endpoints return paginated results in this envelope: ```json { "data": [...], "pagination": { "page": 1, "page_size": 25, "total_count": 342, "total_pages": 14, "has_next": true, "has_previous": false } } ``` Use `?page=2&page_size=50` query parameters. Maximum page size is 100. ## Error Responses All errors conform to [RFC 9457 Problem Details](https://www.rfc-editor.org/rfc/rfc9457) with `Content-Type: application/problem+json`: ```json { "type": "https://closient.com/docs/errors/not_found", "title": "Not Found", "status": 404, "detail": "The requested resource was not found.", "error_code": "not_found", "retryable": false, "timestamp": "2026-03-31T12:00:00+00:00" } ``` Common error codes: `unauthorized` (401), `forbidden` (403), `not_found` (404), `validation_error` (422), `rate_limited` (429), `internal_error` (500). termsOfService: https://www.closient.com/terms/ servers: - url: https://www.closient.com security: [] externalDocs: description: Closient Documentation url: https://docs.closient.com paths: /epcis/api/2.0/verification/serial: get: tags: - EPCIS 2.0 summary: Verify a serialized unit for returns description: >- Decide whether a scanned GTIN + serial was sold by the authenticated organization, when, under which transaction, and whether it has already been returned. Intended for a return desk scanner or POS plugin: one call, one decision object. Decisions are computed **only** from the querying organization's own EPCIS events — another retailer's sale of the same GTIN + serial is never visible here, and a unit this organization has no events for is reported as ``unknown_serial`` rather than falling back to anyone else's history. Recall status is the one deliberate exception: it is public product-safety information, so an open recall covering the unit is reported regardless of which organization published it. The lifecycle states ride GS1 CBV 2.0 dispositions — ``retail_sold`` for a sale (bizStep ``retail_selling``) and ``returned`` for a return (bizStep ``returning``). Caller must hold an OWNER or MANAGER membership on the organization. operationId: apps_epcis_api_verification_epcis_verify_serial parameters: - in: query name: gtin schema: description: >- GTIN-8/12/13/14 of the scanned unit. Normalized to GTIN-14; check digit is validated. pattern: ^[0-9]{8}$|^[0-9]{12,14}$ title: Gtin type: string required: true description: >- GTIN-8/12/13/14 of the scanned unit. Normalized to GTIN-14; check digit is validated. - in: query name: serial schema: description: GS1 AI(21) serial number of the scanned unit. maxLength: 255 minLength: 1 title: Serial type: string required: true description: GS1 AI(21) serial number of the scanned unit. responses: '200': description: OK content: application/json: schema: $ref: '#/components/schemas/SerialVerificationSchema' '400': description: Bad Request content: application/problem+json: schema: $ref: '#/components/schemas/ErrorOut' '401': description: Unauthorized content: application/problem+json: schema: $ref: '#/components/schemas/ErrorOut' '403': description: Forbidden content: application/problem+json: schema: $ref: '#/components/schemas/ErrorOut' '404': description: Not Found content: application/problem+json: schema: $ref: '#/components/schemas/ErrorOut' '405': description: Method Not Allowed content: application/problem+json: schema: $ref: '#/components/schemas/ErrorOut' '422': description: Unprocessable Content content: application/problem+json: schema: $ref: '#/components/schemas/ErrorOut' '429': description: Too Many Requests content: application/problem+json: schema: $ref: '#/components/schemas/ErrorOut' security: - APIKeyHeaderAuth: [] - OAuthTokenAuth: [] - CookieGatedSessionAuth: [] components: schemas: SerialVerificationSchema: description: Decision object for one GTIN + serial. examples: - decision: sold gtin: '00614524740108' lot: L2847 sale_transaction_reference: TXN-88213 serial: ABC123XYZ sold_at: '2026-07-15T14:32:00Z' properties: decision: $ref: '#/components/schemas/VerificationDecisionEnum' description: >- The verdict. ``recalled_lot`` outranks the lifecycle states — when a unit is under an open recall it is reported as such whether or not it was sold, and the sale/return fields below remain populated. gtin: description: Normalized GTIN-14 the decision was computed for. title: Gtin type: string serial: description: GS1 AI(21) serial number the decision was computed for. title: Serial type: string lot: anyOf: - type: string - type: 'null' description: GS1 AI(10) lot identifier recorded for this unit, when known. title: Lot sold_at: anyOf: - format: date-time type: string - type: 'null' description: Event time of the sale, when this organization has recorded one. title: Sold At sale_transaction_reference: anyOf: - type: string - type: 'null' description: >- bizTransaction identifier carried on the sale event, scoped to this organization. title: Sale Transaction Reference returned_at: anyOf: - format: date-time type: string - type: 'null' description: >- Event time of the recorded return, when the unit has already come back. title: Returned At recall: anyOf: - $ref: '#/components/schemas/RecallNoticeSchema' - type: 'null' description: Populated only when ``decision`` is ``recalled_lot``. required: - decision - gtin - serial title: SerialVerificationSchema type: object ErrorOut: description: |- RFC 9457 Problem Details response. All API errors are returned in this format with Content-Type: application/problem+json. examples: - detail: The requested resource was not found. error_code: not_found retryable: false status: 404 timestamp: '2026-03-31T12:00:00+00:00' title: Not Found type: https://closient.com/docs/errors/not_found - detail: Validation error. details: - loc: - body - name msg: Field required type: missing error_code: validation_error retryable: false status: 422 timestamp: '2026-03-31T12:00:00+00:00' title: Validation Error type: https://closient.com/docs/errors/validation_error - detail: Rate limit exceeded. Please try again later. error_code: rate_limited retry_after: 31 retryable: true status: 429 timestamp: '2026-03-31T12:00:00+00:00' title: Rate Limited type: https://closient.com/docs/errors/rate_limited properties: type: description: URI reference identifying the error type. title: Type type: string title: description: Short human-readable summary of the error. title: Title type: string status: description: HTTP status code. title: Status type: integer detail: description: Human-readable explanation of this specific occurrence. title: Detail type: string error_code: description: Machine-readable error code (e.g. not_found, unauthorized). title: Error Code type: string retryable: default: false description: Whether retrying the same request can succeed. title: Retryable type: boolean timestamp: description: ISO 8601 timestamp of when the error occurred. title: Timestamp type: string retry_after: anyOf: - type: integer - type: 'null' description: Seconds to wait before retrying (when applicable). title: Retry After owner_action_required: anyOf: - type: boolean - type: 'null' description: Whether the error requires account owner intervention. title: Owner Action Required details: description: Additional context (validation errors, etc.). title: Details required: - type - title - status - detail - error_code - timestamp title: ErrorOut type: object VerificationDecisionEnum: description: |- Verdict for one GTIN + serial verification. Exactly one value is returned per call. ``RECALLED_LOT`` is evaluated first and outranks every lifecycle state — see :func:`verify_serial`. enum: - sold - already_returned - never_sold - unknown_serial - recalled_lot title: VerificationDecisionEnum type: string RecallNoticeSchema: description: The open recall that produced a ``recalled_lot`` decision. examples: - lot: L2847 recall_id: RCL-2026-04821 severity: FDA Class II title: 'Voluntary recall: undeclared allergen' properties: recall_id: description: Identifier of the open recall covering this unit. title: Recall Id type: string title: description: Human-readable recall title. title: Title type: string severity: description: Recall severity classification (e.g. FDA Class I/II/III). title: Severity type: string lot: description: Lot identifier of the unit that matched the recall's scope. title: Lot type: string required: - recall_id - title - severity - lot title: RecallNoticeSchema type: object securitySchemes: APIKeyHeaderAuth: type: apiKey in: header name: X-API-Key OAuthTokenAuth: type: http scheme: bearer CookieGatedSessionAuth: type: apiKey in: cookie name: sessionid ````