> ## Documentation Index > Fetch the complete documentation index at: https://andcze.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # Validate a discount code against the cart > Server-side quote using the same function as checkout (variant/method price → discount → VAT). For several lines the discount is computed once per cart and split proportionally over the lines the code covers (`lines[].discountShare`, adding up to the cent). An invalid code is `valid: false`, not an error. Does not reserve a code use. ## OpenAPI ````yaml /openapi.en.json post /api/v2/storefront/v1/shops/{shopId}/discounts/validate openapi: 3.0.0 info: title: ItemShop v2 API description: >- REST API platformy ItemShop v2 (NestJS + Fastify). Wszystkie ścieżki mają prefiks /api/v2. version: 2.0.0 contact: {} servers: - url: https://itemshop.dev description: Production (API under /api/v2, same origin as the panel) - url: http://localhost:3000 description: Local security: [] tags: [] paths: /api/v2/storefront/v1/shops/{shopId}/discounts/validate: post: tags: - Storefront v1 summary: Validate a discount code against the cart description: >- Server-side quote using the same function as checkout (variant/method price → discount → VAT). For several lines the discount is computed once per cart and split proportionally over the lines the code covers (`lines[].discountShare`, adding up to the cent). An invalid code is `valid: false`, not an error. Does not reserve a code use. operationId: validateDiscount parameters: - name: shopId required: true in: path description: >- Shop ID (ObjectId). Also accepts the `uniqueName`, an active custom domain or `.`. schema: type: string example: 664f1a2b3c4d5e6f7a8b9c0d requestBody: content: application/json: schema: $ref: '#/components/schemas/StorefrontValidateDiscountDto' responses: '200': description: '' content: application/json: schema: $ref: '#/components/schemas/StorefrontDiscountQuoteResponseDto' '400': description: >- `VALIDATION_FAILED`, `CART_EMPTY`, `CART_TOO_LARGE`, `INVALID_QUANTITY`, `PRODUCT_VARIANT_REQUIRED`… content: application/json: schema: $ref: '#/components/schemas/StorefrontErrorDto' '403': description: Origin outside the shop domains (`ORIGIN_NOT_ALLOWED`) content: application/json: schema: $ref: '#/components/schemas/StorefrontErrorDto' '404': description: >- Shop/resource not found or the shop is blocked (`SHOP_NOT_FOUND`, `PRODUCT_NOT_FOUND`, `ORDER_NOT_FOUND`) content: application/json: schema: $ref: '#/components/schemas/StorefrontErrorDto' '429': description: Rate limit exceeded (`RATE_LIMITED`) content: application/json: schema: $ref: '#/components/schemas/StorefrontErrorDto' components: schemas: StorefrontValidateDiscountDto: type: object properties: code: type: string minLength: 1 maxLength: 50 pattern: ^[A-Za-z0-9_-]+$ example: LATO10 items: minItems: 1 maxItems: 20 description: >- Cart lines (1–20). Several lines = a payment group: one order per line and one payment for the total (adr/0002) type: array items: $ref: '#/components/schemas/StorefrontCartItemDto' paymentMethodCode: type: string minLength: 1 maxLength: 100 description: Payment method — the product may have a different price for it example: imoje required: - code - items StorefrontDiscountQuoteResponseDto: type: object properties: success: type: boolean example: true data: $ref: '#/components/schemas/StorefrontDiscountQuoteDto' required: - success - data StorefrontErrorDto: type: object properties: success: type: boolean example: false statusCode: type: number example: 404 code: enum: - VALIDATION_FAILED - BAD_REQUEST - NOT_FOUND - SHOP_NOT_FOUND - PRODUCT_NOT_FOUND - ORDER_NOT_FOUND - PRODUCT_UNAVAILABLE - PRODUCT_VARIANT_REQUIRED - INVALID_PRODUCT_VARIANT - INVALID_QUANTITY - OUT_OF_STOCK - CART_EMPTY - NICK_REQUIRED - EMAIL_REQUIRED - CART_TOO_LARGE - DISCOUNT_INVALID - LEGAL_CONSENT_REQUIRED - LEGAL_DOCUMENTS_CHANGED - SHOP_PAYMENT_NOT_READY - PAYMENT_INIT_FAILED - ORDER_BLOCKED - RETURN_URL_NOT_ALLOWED - VOUCHER_NOT_FOUND - VOUCHER_USED - VOUCHER_EXPIRED - IDEMPOTENCY_KEY_REQUIRED - IDEMPOTENCY_KEY_REUSED - CHECKOUT_ATTEMPT_CLOSED - CHECKOUT_IN_PROGRESS - CAPTCHA_REQUIRED - ORIGIN_NOT_ALLOWED - FORBIDDEN - UNAUTHORIZED - PAYLOAD_TOO_LARGE - CONFLICT - RATE_LIMITED - SERVICE_UNAVAILABLE - INTERNAL_ERROR type: string description: Machine-readable error code — translate UI messages by this example: SHOP_NOT_FOUND message: type: string description: >- Developer message (language not guaranteed; do not show it to buyers) example: Shop not found error: type: string description: Same as `message` (compatibility with the rest of the API) example: Shop not found deprecated: true details: type: object description: Validation details timestamp: type: string format: date-time example: '2026-10-27T12:00:00.000Z' path: type: string example: /api/v2/storefront/v1/shops/moj-sklep required: - success - statusCode - code - message - error - timestamp - path StorefrontCartItemDto: type: object properties: productId: type: string example: 664f1a2b3c4d5e6f7a8b9c0d quantity: type: number minimum: 1 maximum: 100000 example: 1 default: 1 variantId: type: string description: >- `variants[].id` (one of variantId/variant required when pricingMode = variants) example: 664f1a2b3c4d5e6f7a8b9c11 variant: type: string minLength: 1 maxLength: 80 description: Variant name (instead of variantId) example: 30 dni required: - productId StorefrontDiscountQuoteDto: type: object properties: valid: type: boolean example: true code: type: string nullable: true example: LATO10 reason: type: string nullable: true description: Rejection reason (for developers) example: null subtotal: type: number description: Total before discount example: 39.98 discountAmount: type: number example: 4 total: type: number description: Amount due (after discount and VAT) — exactly what checkout charges example: 35.98 currency: type: string example: PLN lines: description: Per-line quote in `items[]` order; the line totals add up to `total` type: array items: $ref: '#/components/schemas/StorefrontQuoteLineDto' required: - valid - code - reason - subtotal - discountAmount - total - currency - lines StorefrontQuoteLineDto: type: object properties: productId: type: string example: 664f1a2b3c4d5e6f7a8b9c0d subtotal: type: number description: Before discount example: 19.99 discountShare: type: number description: >- This line's share of the cart discount (proportional to value, to the cent) example: 2 total: type: number description: Amount due for the line (after discount and VAT) example: 17.99 required: - productId - subtotal - discountShare - total ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.