> ## Documentation Index
> Fetch the complete documentation index at: https://docs.agentaos.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Retrieve a checkout

> Adds a computed `amount` (the effective price: `amount_override`, else the linked payment link's amount), plus the link's own `link_amount`/`link_currency`/`link_description`, and the checkout's `transactions` and `invoices` arrays.



## OpenAPI

````yaml GET /gateway/sessions/{sessionId}
openapi: 3.1.0
info:
  title: AgentaOS Gateway API
  version: 1.0.0
  description: >-
    The AgentaOS REST API: payment links, checkouts, subscriptions, customers,
    invoices, and the unified transactions feed. This is the same API the
    TypeScript SDK (`@agentaos/pay`) and the `agenta` CLI call underneath.


    ## Money model


    - **Decimal currency units (`number`)**: a plain `amount` field (on a create
    body, a Payment Link, a Checkout's `amount_override`, or an Invoice's
    `amount`/`fiat_amount`/`tax_amount`) is in currency units. `49.99` means EUR
    49.99, never cents.

    - **Integer minor units (`number`)**: exactly one field breaks that rule:
    `unitAmountMinor` on a Subscription. It is an integer count of the smallest
    currency unit (`1999` means EUR 19.99), named with a `Minor` suffix
    specifically so it is never confused with a plain `amount`. The `money`
    object on Transactions and the `earnings` object on a retrieved Invoice are
    also integer minor units, computed server-side.

    - **String, on webhooks**: the `amount` inside a webhook payload's `data`
    object is a string (e.g. `"49.99"`), since JSON numbers silently drop
    trailing zeros and this value must round-trip exactly for accounting.


    ## Naming convention


    Most response fields mirror the underlying database column and are
    `snake_case` (`created_at`, `seller_mode`, `buyer_email`, ...). A small
    number of computed convenience fields are camelCase with no snake_case
    equivalent: `checkoutUrl` on Checkouts and Payment Links, `sellerMode` on
    Payment Links specifically, `money` on Transactions, and `earnings` on a
    single retrieved Invoice. Two resources (Subscriptions and Customers) are
    fully camelCase end to end.


    ## Pagination


    Every list endpoint takes `limit` and `offset` and returns `{ items, total,
    hasMore }`. `hasMore` is computed server-side (`offset + items.length <
    total`); never derive it client-side.
  contact:
    name: AgentaOS
    url: https://agentaos.ai
  license:
    name: Proprietary
    url: https://agentaos.ai
servers:
  - url: https://api.agentaos.ai/api/v1
    description: Production
security:
  - ApiKeyAuth: []
tags:
  - name: Payment Links
    description: >-
      Reusable, shareable payment products: a fixed amount and description
      behind one URL.
  - name: Checkouts
    description: >-
      One attempt to collect one payment, standalone or built from a payment
      link. Wire path is `/gateway/sessions`; the SDK and CLI call this resource
      "checkout".
  - name: Subscriptions
    description: >-
      Merchant-side read and management surface for recurring plans. Created
      automatically when a buyer pays a `type: subscription` payment link.
  - name: Customers
    description: 'Read-only surface: everyone who has paid you or been sent an invoice.'
  - name: Invoices
    description: >-
      Every checkout issues an invoice. List, retrieve, void, export, and
      download PDFs/receipts.
  - name: Transactions
    description: >-
      The unified activity feed: every inbound payment and outbound send, across
      every rail, in one list.
paths:
  /gateway/sessions/{sessionId}:
    get:
      tags:
        - Checkouts
      summary: Retrieve a checkout
      description: >-
        Adds a computed `amount` (the effective price: `amount_override`, else
        the linked payment link's amount), plus the link's own
        `link_amount`/`link_currency`/`link_description`, and the checkout's
        `transactions` and `invoices` arrays.
      operationId: getCheckout
      parameters:
        - $ref: '#/components/parameters/SessionId'
      responses:
        '200':
          description: The checkout, with computed amount and related rows.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/CheckoutDetail'
        '401':
          $ref: '#/components/responses/Unauthorized'
        '403':
          $ref: '#/components/responses/Forbidden'
        '404':
          $ref: '#/components/responses/NotFound'
components:
  parameters:
    SessionId:
      name: sessionId
      in: path
      required: true
      description: The public `session_id` (not the internal `id` UUID).
      schema:
        type: string
  schemas:
    CheckoutDetail:
      allOf:
        - $ref: '#/components/schemas/Checkout'
        - type: object
          properties:
            amount:
              type:
                - number
                - 'null'
              description: >-
                Computed effective price: amount_override, else the linked
                payment link's amount.
            link_amount:
              type:
                - number
                - 'null'
            link_currency:
              type:
                - string
                - 'null'
            link_description:
              type:
                - string
                - 'null'
            transactions:
              type: array
              items:
                $ref: '#/components/schemas/LinkTransactionRow'
            invoices:
              type: array
              items:
                $ref: '#/components/schemas/Invoice'
          required:
            - amount
            - link_amount
            - link_currency
            - link_description
            - transactions
            - invoices
    Checkout:
      type: object
      additionalProperties: true
      properties:
        id:
          type: string
          format: uuid
          description: Internal checkout UUID.
        payment_link_id:
          type:
            - string
            - 'null'
          format: uuid
        org_id:
          type: string
          format: uuid
        session_id:
          type: string
          description: >-
            Public ID, used in the checkout URL and as the path parameter for
            every other call on this resource.
        idempotency_key:
          type:
            - string
            - 'null'
        amount_override:
          type:
            - number
            - 'null'
          description: Set only if you passed amount or amountOverride at create.
        currency:
          type: string
        metadata:
          type: object
        webhook_url:
          type:
            - string
            - 'null'
        success_url:
          type:
            - string
            - 'null'
        cancel_url:
          type:
            - string
            - 'null'
        tax_rate_id:
          type:
            - string
            - 'null'
          format: uuid
        supported_networks:
          type: array
          items:
            type: string
        expires_at:
          type: string
          format: date-time
        status:
          type: string
          enum:
            - open
            - completed
            - expired
            - cancelled
        created_at:
          type: string
          format: date-time
        updated_at:
          type: string
          format: date-time
        seller_mode:
          type: string
          enum:
            - mor
            - crypto
        environment:
          type: string
          enum:
            - test
            - live
        checkoutUrl:
          type: string
          description: Send your buyer here. Computed, camelCase.
        invoiceId:
          type:
            - string
            - 'null'
          format: uuid
          description: >-
            Set once an invoice has been issued for this session; null until
            then.
        invoiceNumber:
          type:
            - string
            - 'null'
      required:
        - id
        - payment_link_id
        - org_id
        - session_id
        - idempotency_key
        - amount_override
        - currency
        - metadata
        - webhook_url
        - success_url
        - cancel_url
        - tax_rate_id
        - supported_networks
        - expires_at
        - status
        - created_at
        - updated_at
        - seller_mode
        - environment
        - checkoutUrl
    LinkTransactionRow:
      type: object
      description: >-
        A raw transaction row as nested under a Payment Link or Checkout detail
        response: same shape as a Transaction, but without the computed `money`
        breakdown.
      additionalProperties: true
      properties:
        id:
          type: string
          format: uuid
        direction:
          type: string
          enum:
            - inbound
            - outbound
        status:
          type: string
        amount:
          type: number
        payment_method:
          type:
            - string
            - 'null'
        created_at:
          type: string
          format: date-time
      required:
        - id
        - direction
        - status
        - amount
        - created_at
    Invoice:
      type: object
      additionalProperties: true
      properties:
        id:
          type: string
          format: uuid
        invoice_number:
          type: string
          description: Human-readable, e.g. INV-2026-0142.
        transaction_id:
          type:
            - string
            - 'null'
          format: uuid
          description: Linked settled transaction, once paid.
        session_id:
          type:
            - string
            - 'null'
          description: Linked checkout.
        amount:
          type: number
          description: Currency units.
        currency:
          type: string
        payment_token:
          type: string
          description: What the buyer paid (or will pay) with.
        status:
          type: string
          enum:
            - issued
            - paid
            - voided
          description: issued (created, not yet paid), paid (payment settled), or voided.
        fiat_amount:
          type:
            - number
            - 'null'
          description: EUR/USD equivalent, for stablecoin payments.
        fiat_currency:
          type:
            - string
            - 'null'
          enum:
            - EUR
            - USD
            - null
        exchange_rate:
          type:
            - number
            - 'null'
          description: Rate applied at settlement.
        exchange_rate_source:
          type:
            - string
            - 'null'
        tax_rate:
          type:
            - number
            - 'null'
          description: Applied rate, e.g. 19 for 19%.
        tax_amount:
          type:
            - number
            - 'null'
          description: Currency units.
        tax_name:
          type:
            - string
            - 'null'
          description: e.g. DE VAT.
        tax_inclusive:
          type:
            - boolean
            - 'null'
          description: Whether amount already includes tax.
        merchant_name:
          type:
            - string
            - 'null'
          description: Seller name on the document.
        buyer_email:
          type:
            - string
            - 'null'
        buyer_name:
          type:
            - string
            - 'null'
        buyer_company:
          type:
            - string
            - 'null'
        buyer_country:
          type:
            - string
            - 'null'
          description: ISO 3166-1 alpha-2.
        buyer_vat:
          type:
            - string
            - 'null'
        tx_hash:
          type:
            - string
            - 'null'
          description: On-chain hash, for crypto payments.
        issued_at:
          type: string
          format: date-time
        voided_at:
          type:
            - string
            - 'null'
          format: date-time
        created_at:
          type: string
          format: date-time
      required:
        - id
        - invoice_number
        - transaction_id
        - session_id
        - amount
        - currency
        - payment_token
        - status
        - fiat_amount
        - fiat_currency
        - exchange_rate
        - exchange_rate_source
        - tax_rate
        - tax_amount
        - tax_name
        - tax_inclusive
        - merchant_name
        - buyer_email
        - buyer_name
        - buyer_company
        - buyer_country
        - buyer_vat
        - tx_hash
        - issued_at
        - voided_at
        - created_at
    Error:
      type: object
      description: >-
        Every non-2xx response is JSON in this shape. Every response (success or
        error) also carries an `x-request-id` response header; send that header
        on your request to have your own id echoed back, otherwise the server
        mints one. On errors the same id is repeated in the `requestId` body
        field.
      properties:
        statusCode:
          type: integer
          description: Same as the HTTP status code.
        message:
          description: >-
            Human-readable. A validation failure (400) returns an array of
            per-field messages instead of one string.
          anyOf:
            - type: string
            - type: array
              items:
                type: string
        errors:
          type: array
          description: >-
            Present on 400 validation failures: one entry per invalid field. The
            flat human-readable strings stay in `message` for back-compat; this
            is the machine-readable, per-field view.
          items:
            type: object
            properties:
              field:
                type: string
                description: >-
                  Name of the invalid field, dot-notated for nested properties
                  (e.g. `checkoutFields.0.type`).
              message:
                type: string
                description: Validation messages for that field, joined with `, `.
            required:
              - field
              - message
        requestId:
          type: string
          description: >-
            Correlation id, identical to the `x-request-id` response header.
            Include it when contacting support. On success it is available on
            the header only, not the body.
        timestamp:
          type: string
          format: date-time
      required:
        - statusCode
        - message
        - timestamp
  responses:
    Unauthorized:
      description: Missing or invalid `x-api-key`.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
          example:
            statusCode: 401
            message: Invalid API key
            timestamp: '2026-08-06T12:00:00.000Z'
    Forbidden:
      description: The key is valid but the resource belongs to a different organization.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
          example:
            statusCode: 403
            message: Payment link belongs to another organization
            timestamp: '2026-08-06T12:00:00.000Z'
    NotFound:
      description: >-
        Resource not found (or not visible to your key; the two are not
        distinguished).
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
          example:
            statusCode: 404
            message: Payment link not found
            timestamp: '2026-08-06T12:00:00.000Z'
  securitySchemes:
    ApiKeyAuth:
      type: apiKey
      in: header
      name: x-api-key
      description: >-
        Your secret key, from app.agentaos.ai -> Settings -> Developers -> API
        Keys. The key's prefix is both its identity and its environment:
        `sk_test_...` (sandbox, free, no verification) or `sk_live_...` (real
        money, requires business verification). A missing or invalid key returns
        401.

````