> ## Documentation Index > Fetch the complete documentation index at: https://docs.arcuserp.com/llms.txt > Use this file to discover all available pages before exploring further. # Add a component to a kit/box product > Adds a component product to a kit product, specifying the quantity of the component required to build one kit unit. The parent product must have `product_type: kit`; supplying a non-kit parent returns `code: not_a_kit`. Duplicate component additions are rejected with `code: component_already_exists`. Requires `products:write` scope. ## OpenAPI ````yaml /openapi.yaml post /products/{id}/components openapi: 3.1.0 info: title: Arcus ERP Public API version: 1.0.0 description: > Arcus ERP public REST API. Designed for external integrations and data migration. **Authentication.** Bearer token (API key) via the `Authorization` header. Format: `Authorization: Bearer ark_live_ent__` (or `ark_test_*` for sandbox). API keys are issued per-entity in **Settings > Developers > API Keys**. **Entity scoping.** The entity is encoded in the API key prefix; routes are flat (e.g. `/v1/accounts`, `/v1/orders`, `/v1/products`). A small set of platform endpoints (migration, reconciliation, events, webhook endpoints, API keys) use the `/v1/entities/{entity_id}/...` form -- those are noted in their tags. **Key capabilities.** - Related-resource hydration via `?expand[]=` (see `x-arcus-expand` on each resource). - Cursor-based pagination (`starting_after` / `ending_before` / `limit`). - Idempotency via the `Idempotency-Key` header. - Webhook events for asynchronous notification. - Conditional requests / ETag for cache validation. servers: - url: https://api.arcuserp.com/v1 description: Arcus ERP API (accepts both live `ark_live_*` and test `ark_test_*` keys) - url: https://dev-api.arcuserp.com/v1 description: >- Dev sandbox API (test-only data, accepts `ark_test_*` keys against dev RDS) security: [] paths: /products/{id}/components: post: tags: - Products summary: Add a component to a kit/box product description: > Adds a component product to a kit product, specifying the quantity of the component required to build one kit unit. The parent product must have `product_type: kit`; supplying a non-kit parent returns `code: not_a_kit`. Duplicate component additions are rejected with `code: component_already_exists`. Requires `products:write` scope. operationId: addKitComponent parameters: - name: id in: path required: true schema: type: string format: uuid - $ref: '#/components/parameters/IdempotencyKey' requestBody: required: true content: application/json: schema: type: object required: - component_product_id - quantity_per_kit properties: component_product_id: type: string format: uuid quantity_per_kit: type: number minimum: 0 sort_order: type: integer description: Display order of the component within the kit. default: 0 notes: type: string nullable: true external_source: type: string nullable: true description: >- Source-system tag for historical migration (e.g. 'bubble_io', 'versa_cloud'). external_id: type: string nullable: true description: Source-system row id, persisted for batch traceability. migration_batch_id: type: string format: uuid nullable: true description: Optional migration-wave identifier, persisted on the row. imported_at: type: string format: date-time nullable: true description: >- Source record timestamp; preserve the origin system's created_at for audit fidelity. responses: '201': description: Component added content: application/json: schema: type: object '400': $ref: '#/components/responses/Error' '401': $ref: '#/components/responses/Error' '403': $ref: '#/components/responses/Error' security: - ApiKeyAuth: - products:write components: parameters: IdempotencyKey: name: Idempotency-Key in: header required: false description: | Client-generated unique key for idempotent POST/PATCH/DELETE operations. Alias for the Idempotency parameter. Max 255 chars. On retry with the same key, the original response is returned without re-executing the operation. Keys expire after 24 hours. schema: type: string maxLength: 255 responses: Error: description: Error response (400/401/403/404/409/422/429/500) content: application/json: schema: $ref: '#/components/schemas/ErrorEnvelope' schemas: ErrorEnvelope: type: object description: | Canonical error response envelope. All API errors use this shape. required: - error - code properties: error: type: string description: Machine-readable error key example: not_found code: type: string description: Machine-readable error code (often same as error) example: not_found type: type: string enum: - validation_error - permission_error - not_found - conflict - rate_limit - internal - expand_error - not_implemented example: not_found hint: type: string description: Human-readable one-sentence explanation (English) example: >- The requested order does not exist or does not belong to this entity. param: type: string description: The parameter that caused the error, if applicable example: expand[0] required: type: string description: The scope required (only on insufficient_scope errors) example: accounts:read request_id: type: string description: >- Unique request ID for support tracing (maps to CloudWatch log stream) example: req_abc123 securitySchemes: ApiKeyAuth: type: http scheme: bearer description: | API key issued per entity via Settings > Developers > API Keys. Each key carries scopes (e.g. orders:read, products:write). Bearer token format: Authorization: Bearer ark_live_ent__ Test keys use ark_test_ent__. Both are issued per entity via Settings > Developers > API Keys. ````