> ## Documentation Index > Fetch the complete documentation index at: https://docs.famulor.io/llms.txt > Use this file to discover all available pages before exploring further. # Review subscription change > Reviews an existing subscription change without submitting the change or charging a card. Provide the complete desired plan and add-on selection. Returns estimated tax, the amount due, masked eligible methods and short-lived references. This operation does not create new subscriptions or checkouts. Resolve pending invoices in the app before requesting another review. Requires a user-owned credential with billing:write scope and owner, admin or billing access in the active workspace. API Access must be enabled. ## OpenAPI ````yaml /api-reference/openapi.json post /billing/subscription-change/review openapi: 3.1.0 info: title: Famulor API version: 1.0.0 description: >- REST API for Famulor. Authenticate with an API key (`fam_...`, created under **Settings → API Keys**) or an OAuth 2.0 access token (`fam_at_...`) as a Bearer token. Every response uses a consistent envelope: `{ "data": ... , "meta": { ... } }` on success and `{ "error": { "code", "message" } }` on failure. List endpoints paginate with `?limit=` (default 50, max 200) and `?offset=`; `meta.pagination.total` carries the total match count. REST operations require API Access through the workspace plan or a recurring add-on. Without it, regular operations return `403 api_access_required`. The invoice-payment and billing-portal operations remain available with a valid `billing:write` credential after a failed plan payment so an authorized owner, admin, or billing member can recover billing. The same customer-facing capabilities are available as MCP tools at `https://app.famulor.io/mcp` (Model Context Protocol, streamable HTTP) using the same credentials, scopes, and workspace access. MCP availability is controlled separately by Connect AI / MCP, not by API Access. servers: - url: https://app.famulor.io/api/v1 description: Hosted platform. - url: https://{domain}/api/v1 description: White-label tenant domain — same paths, tenant branding. variables: domain: default: app.famulor.io description: Your white-label tenant domain. security: - bearerAuth: [] tags: - name: Account description: Self-inspection of the calling credential. - name: Migrations description: Preview and import data from supported legacy platforms. - name: Assistants description: Create and manage voice assistants. - name: Tools description: >- Reusable tools (HTTP APIs and external MCP servers) assistants can call mid-conversation. - name: Voices description: Browse the text-to-speech voice library. - name: Calls description: Start outbound calls and read call history, transcripts and recordings. - name: History description: Unified conversation history across calls, messaging and assistant emails. - name: Campaigns description: Outbound calling campaigns with a compliant power dialer. - name: Leads description: Manage Audience contacts across campaigns, channels and Call QA metrics. - name: Segments description: >- Saved, dynamic lead filters — reusable audience definitions used for Audience search and campaign lead assignment. - name: Suppression description: Cross-channel marketing opt-outs and active workspace suppression records. - name: Callbacks description: >- Scheduled callbacks booked by the Schedule callback tool across voice, chat, and email. - name: Phone Numbers description: Marketplace numbers and customer-provided numbers. - name: Famulor Loop description: >- Personal business-phone access, directory, presence, devices, and Loop call recents. - name: SIP Trunks description: Bring your own SIP provider and numbers. - name: Carrier Connections description: Connect a supported carrier account and import its existing phone numbers. - name: Knowledge Bases description: RAG knowledge bases and documents for assistants. - name: Settings description: Workspace-level settings such as caller-memory defaults. - name: Billing description: Balance and minutes ledger of the key owner. - name: Automations description: >- Native workspace automations — list, create, update, trigger. Plan gate: automation_platform. - name: Milian Missions description: Recurring jobs that Milian runs unattended on schedule. - name: Integrations description: >- Calendar integrations (Cal.com, Calendly, Acuity Scheduling, Google Calendar, Outlook, native booking engine). Assign them to assistants to provide availability and booking tools, plus provider-supported appointment lookup, cancellation, and rescheduling. - name: Bookings description: >- Native booking engine — event types with weekly availability, public booking pages at /book/{workspace}/{slug}, and the bookings they produce. - name: Dashboards description: >- Custom analytics dashboards, reusable widgets, and tenant-scoped performance analytics. Requires the custom_dashboards plan feature. - name: Catalog description: >- Read-only platform catalogs — available models, supported assistant languages, and prompt templates. - name: Simulations description: Assistant simulation tests (plan-gated). - name: Versions description: Assistant configuration version history. - name: Caller IDs description: Outbound caller ID verification. - name: Widgets description: Web widget connectors. - name: Messaging description: >- Telegram, Slack, and Messenger text bots linked to assistants (Chat SDK). Includes conversation delay, inactivity end, and conversation-ended webhooks. - name: QA description: Cohort AI Quality Assurance runs over call transcripts. - name: White Label description: >- Manage white-label customer accounts, defaults, credit transfers and customer plan offers. Each endpoint documents its required scope and workspace eligibility. - name: API Keys description: >- Self-service API keys for the calling workspace or a same-brand workspace where the credential's user is owner/admin. A key can only mint further keys with a scope subset of its own. - name: Workspaces description: >- List visible workspaces, create an additional workspace for the key owner, and mint a dedicated credential for a selected owner/admin workspace. - name: SMS description: Outbound SMS from workspace phone numbers. paths: /billing/subscription-change/review: post: tags: - Billing summary: Review subscription change description: >- Reviews an existing subscription change without submitting the change or charging a card. Provide the complete desired plan and add-on selection. Returns estimated tax, the amount due, masked eligible methods and short-lived references. This operation does not create new subscriptions or checkouts. Resolve pending invoices in the app before requesting another review. Requires a user-owned credential with billing:write scope and owner, admin or billing access in the active workspace. API Access must be enabled. operationId: reviewSubscriptionPaymentChange requestBody: required: true content: application/json: schema: type: object additionalProperties: false required: - addon_ids - interval properties: plan_id: type: string format: uuid description: Target plan. Omit only for an add-on-only subscription. addon_ids: type: array maxItems: 100 items: type: string format: uuid description: >- Complete desired add-on selection, including every add-on to keep. addon_quantities: type: object additionalProperties: type: integer minimum: 1 maximum: 100000 interval: type: string enum: - monthly - yearly responses: '200': description: Review subscription change. content: application/json: schema: type: object required: - data properties: data: type: object required: - review_ref - expires_at - amount_due - tax_amount - currency - summary - payment_required - methods - billing_url properties: review_ref: type: string description: >- Opaque reference to the exact selection, workspace, user and maximum amount reviewed. Expires after 15 minutes. expires_at: type: string format: date-time amount_due: type: integer description: >- Maximum reviewed amount due now, in the currency minor unit. A refreshed lower amount is allowed. tax_amount: type: integer description: Estimated tax in the currency minor unit. currency: type: string description: Three-letter currency code. summary: type: string payment_required: type: boolean methods: type: array items: type: object properties: payment_method_ref: type: string description: >- Opaque reference bound to this review and authorized user. type: type: string brand: type: string nullable: true last4: type: string nullable: true exp_month: type: integer nullable: true exp_year: type: integer nullable: true is_default: type: boolean billing_url: type: string format: uri description: >- Open billing in the app to manage methods or resolve a pending payment. '400': description: Invalid request or missing explicit confirmation. '401': $ref: '#/components/responses/Unauthorized' '403': $ref: '#/components/responses/Forbidden' '409': description: >- Review expired, terms changed, method unavailable or billing needs attention. '429': $ref: '#/components/responses/RateLimited' components: responses: Unauthorized: description: Missing, invalid, expired or revoked API key / access token. content: application/json: schema: $ref: '#/components/schemas/ErrorEnvelope' example: error: code: unauthorized message: Invalid API key. Forbidden: description: >- The credential lacks the required scope or role, or the workspace does not have the required capability. content: application/json: schema: $ref: '#/components/schemas/ErrorEnvelope' examples: scopeDenied: summary: Required scope is missing value: error: code: forbidden message: >- This API key is missing the required scope "assistants:write". apiAccessRequired: summary: API Access is not available value: error: code: api_access_required message: >- API Access is not available for this workspace. Review Settings → Plan. RateLimited: description: Too many requests. Retry after the indicated delay. headers: Retry-After: description: Seconds to wait before retrying. schema: type: integer minimum: 1 content: application/json: schema: $ref: '#/components/schemas/ErrorEnvelope' example: error: code: rate_limited message: Too many requests. Retry after the indicated delay. schemas: ErrorEnvelope: type: object description: Error envelope returned by every /api/v1 endpoint on failure. required: - error properties: error: type: object required: - code - message properties: code: type: string enum: - unauthorized - forbidden - api_access_required - not_found - invalid_request - rate_limited - conflict - telephony_configuration_error - telephony_unavailable - destination_forbidden - internal_error description: Stable, machine-readable error code. message: type: string description: Human-readable description of the error. securitySchemes: bearerAuth: type: http scheme: bearer bearerFormat: API key description: >- API key (`fam_...`, created under **Settings → API Keys**) or an OAuth 2.0 access token (`fam_at_...`). REST operations also require API Access for the credential's workspace. Keys can be restricted to scopes such as `assistants:read`, `calls:write`, `campaigns:write`, `automations:read`, `dashboards:read`, `dashboards:write`, `leads:write`, `segments:write`, `loop:read`, `loop:write`, `phone_numbers:write`, `sip_trunks:write`, `knowledge:write`, `voices:read`, `billing:read`, `billing:write`, `settings:write`, `platform:read`, `platform:write`; a `*:write` scope implies the matching `*:read`. Automation and dashboard endpoints also accept the legacy `calls:*` scope. Keys without scope restrictions have full access within the workspace's available capabilities. ````