SMKlog Checkout API

openapi: 3.2.0
info:
  title: SMKlog Quote Checkout API
  version: 1.4.0
  summary: Live parcel rates from a US origin, a checkout handed to a human, and where that checkout stands.
  description: 'Live parcel rates from USPS, UPS, FedEx and DHL Express for a single shipment sent from a US origin: inside the US, or to Canada, the UK, Germany or Australia.'
  termsOfService: https://smklog.com/terms
  contact:
    name: SMKlog
    email: info@smklog.com
    url: https://smklog.com/developers/
  x-publisher: SMKlog (SMKLOG-2022 LLC)
servers:
- url: https://quote-api.smklog.com
  description: 'Production. There is no sandbox host: quoting is free and read-only, so production is the place to try it.'
security:
- {}
- clientCredentials:
  - quote
tags:
- name: Checkout
  description: Agent-prepared payment sessions completed by a human on smklog.com.
paths:
  /agent/checkout-session:
    post:
      operationId: createPaymentSession
      tags:
      - Checkout
      summary: Create a payment session for one parcel label (MPP intent "session")
      description: 'Prices the shipment live, anchors the amount to one service, and returns a handoff URL opening the SMKlog checkout prefilled with the shipment. The human confirms the contents certification and the carrier-adjustment consent there and pays on Stripe hosted checkout. This operation never charges: the agent prepares, the human pays. Pass the quote_id from getParcelQuote and the session reuses that quote instead of spending a second carrier call.'
      x-payment-info:
        intent: session
        method: stripe
        amount: '0'
        currency: USD
        description: Creating the session is free. The label amount is set by the live quote in the response and paid by the human on Stripe hosted checkout behind the site consent gates; no autonomous charge is possible through this API.
        offers:
        - intent: session
          method: stripe
          amount: null
          currency: USD
          description: Amount is set by the live quote returned in the response; null per the draft means dynamic pricing.
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/CheckoutSessionRequest'
            examples:
              fromQuote:
                summary: Reuse a quote_id (no second carrier call)
                value:
                  quote_id: q_8f3c2e1a4b7d
                  service: USPS Ground Advantage
              fromShipment:
                summary: Price live and open checkout in one call
                value:
                  product: Yamaha FG800 acoustic guitar in a hard case
                  from_zip: '07102'
                  to_zip: '30303'
                  to_country: US
                  quantity: 1
      responses:
        '200':
          description: 'The session: intent, method, amount, currency, service, handoff_url, session_id, note. Keep session_id for getCheckoutStatus.'
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/CheckoutSession'
              example:
                intent: session
                session_id: as_3f9c1b2e-7d64-4a8e-9c0f-5b2d1e8a7c33
                method:
                - stripe
                - card
                amount: 38.42
                currency: USD
                service: USPS Ground Advantage
                handoff_url: https://smklog.com/assets/calculator?product=Yamaha+FG800+acoustic+guitar+in+a+hard+case&from_postal_code=07102&to_postal_code=30303&agent_session=as_3f9c1b2e-7d64-4a8e-9c0f-5b2d1e8a7c33
                identified_product_title: Yamaha FG800 acoustic guitar in a hard case
                quote_reused: true
                note: 'Live quote at this moment, not a hold. The human confirms the shipping consents and pays on the checkout page. Keep session_id: get_checkout_status reports when the human has paid and when the label exists.'
        '400':
          description: invalid_json or invalid_request — the body is not the documented shape.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Problem'
              example:
                error: invalid_request
                message: JSON object body required.
        '422':
          description: session_failed — unpriceable, restricted, not a parcel, or more than one box.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Problem'
              example:
                error: session_failed
                message: This shipment is past parcel limits; SMKlog sells parcel labels only.
        '429':
          description: rate_limited. Slow down; the same buckets cover /quote and /mcp (about 80 quote requests an hour per client).
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Problem'
              example:
                error: rate_limited
                message: Too many Smart Quote API requests from this client. Try again later.
  /agent/checkout-session/{session_id}:
    get:
      operationId: getCheckoutStatus
      tags:
      - Checkout
      summary: Read where a payment session stands
      description: 'The stage of the checkout a payment session led to: awaiting_checkout, checkout_started, paid, label_ready (with the tracking number), delivered or refunded. Reads SMKlog order records only, no carrier call. Sessions live 30 days; an unknown or expired id answers 404 session_not_found. The answer never carries names, addresses or emails.'
      parameters:
      - name: session_id
        in: path
        required: true
        schema:
          type: string
          pattern: ^as_[A-Za-z0-9-]{8,80}$
        description: The session_id returned by createPaymentSession.
        example: as_3f9c1b2e-7d64-4a8e-9c0f-5b2d1e8a7c33
      responses:
        '200':
          description: session_id, status, created_at, expires_at, amount, currency, service, checkout (order_id, paid, label_ready, carrier, service, tracking_number, tracking_status, estimated_delivery, delivered_at) and next.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/CheckoutStatus'
              example:
                session_id: as_3f9c1b2e-7d64-4a8e-9c0f-5b2d1e8a7c33
                status: label_ready
                created_at: '2026-10-12T15:04:05.000Z'
                expires_at: '2026-11-11T15:04:05.000Z'
                amount: 38.42
                currency: USD
                service: USPS Ground Advantage
                quote_reused: true
                checkout:
                  order_id: c1d2e3f4-5a6b-4c7d-8e9f-0a1b2c3d4e5f
                  started_at: '2026-10-12T15:09:41.000Z'
                  paid: true
                  label_ready: true
                  refunded: false
                  carrier: USPS
                  service: Ground Advantage
                  tracking_number: '9400100000000000000000'
                  tracking_status: in_transit
                  estimated_delivery: '2026-10-16'
                  delivered_at: null
                next: Label bought. Pass tracking_number to track_parcel for scan events.
        '404':
          description: session_not_found — unknown, malformed or expired session_id.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Problem'
              example:
                error: session_not_found
                message: No payment session with this id. Sessions answer for 30 days.
        '429':
          description: rate_limited — 60 checks an hour per client.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Problem'
              example:
                error: rate_limited
                message: Too many Smart Quote API requests from this client. Try again later.
components:
  schemas:
    Problem:
      type: object
      description: 'Every error answer on this host: a stable machine-readable code in error, a sentence for the human in message, and the missing field names when the code is missing_required_fields.'
      required:
      - error
      properties:
        error:
          type: string
          description: 'Stable code: invalid_json, invalid_request, missing_required_fields, product_not_recognized, product_url_not_detected, session_failed, session_not_found, rate_limited, invalid_token'
        message:
          type: string
          description: What went wrong, in a sentence
        missing:
          type: array
          items:
            type: string
          description: Field names still needed, with missing_required_fields and product_not_recognized
    CheckoutSessionRequest:
      type: object
      description: 'The shipment to open a checkout for: a quote_id from a previous quote, or the shipment itself.'
      properties:
        quote_id:
          type: string
          description: The quote_id a getParcelQuote answer carries (the get_parcel_quote tool returns the same handle), valid 15 minutes. When given, the shipment comes from that quote and product, from_zip, to_zip, to_country and quantity are ignored; an expired handle prices the fields live.
        product:
          type: string
          maxLength: 2000
          description: Required unless quote_id is given.
        from_zip:
          type: string
          pattern: ^[0-9]{5}$
          description: 5-digit US ZIP. Required unless quote_id is given.
        to_zip:
          type: string
          maxLength: 12
          description: 5-digit US ZIP, or the destination country's own postal code. Required unless quote_id is given.
        to_country:
          type: string
          enum:
          - US
          - CA
          - GB
          - DE
          - AU
          default: US
          description: Two-letter destination country
        quantity:
          type: integer
          minimum: 1
          default: 1
          description: How many of the item ship together. Default 1. Units that fit one box get a session for that box; more than one box, or a quantity above 1 sent with exact dimensions, returns no session — one label per box, so create one session per box.
        service:
          type: string
          description: Optional service to anchor the amount, matched as a case-insensitive fragment of the display name; cheapest when omitted or unmatched.
    CheckoutStatus:
      type: object
      description: The stage of the checkout a session led to, derived from the order record. Never carries names, addresses or emails.
      required:
      - session_id
      - status
      properties:
        session_id:
          type: string
          description: The session asked about
        status:
          type: string
          enum:
          - awaiting_checkout
          - checkout_started
          - paid
          - label_ready
          - delivered
          - refunded
          description: Stage, in that order
        created_at:
          type: string
          format: date-time
          description: When the session was made
        expires_at:
          type: string
          format: date-time
          description: When the session stops answering
        amount:
          type: number
          description: The amount the session was anchored to, USD
        currency:
          type: string
          enum:
          - USD
          description: ISO currency, USD
        service:
          type: string
          description: The service the session was anchored to
        quote_reused:
          type: boolean
          description: Whether the session reused a quote_id
        checkout:
          type:
          - object
          - 'null'
          description: The checkout the human started, null while awaiting_checkout
          properties:
            order_id:
              type: string
              description: SMKlog order id, the reference for support
            started_at:
              type: string
              format: date-time
              description: When the checkout was created
            paid:
              type: boolean
            label_ready:
              type: boolean
            refunded:
              type: boolean
            carrier:
              type:
              - string
              - 'null'
              description: USPS, UPS, FedEx or DHL
            service:
              type:
              - string
              - 'null'
              description: The service the human actually chose
            tracking_number:
              type:
              - string
              - 'null'
              description: Present from label_ready on
            tracking_status:
              type:
              - string
              - 'null'
              description: Latest carrier status when known
            estimated_delivery:
              type:
              - string
              - 'null'
              description: ISO date when the carrier gives one
            delivered_at:
              type:
              - string
              - 'null'
              format: date-time
        next:
          type: string
          description: What, if anything, the agent should do now
    CheckoutSession:
      type: object
      description: 'A payment session, not a charge: the amount and the handoff URL where the human pays. The amount is a live quote at this moment, not a hold or a reservation, and no money moves until the human completes the page.'
      required:
      - intent
      - amount
      - currency
      - handoff_url
      properties:
        intent:
          type: string
          enum:
          - session
          description: Always "session" — this operation never charges
        session_id:
          type:
          - string
          - 'null'
          pattern: ^as_[A-Za-z0-9-]{8,80}$
          description: Handle for getCheckoutStatus, shaped as_ plus a UUID, good for 30 days. Null only when the session record could not be stored.
        method:
          type: array
          items:
            type: string
          description: Payment rails behind the checkout, e.g. stripe, card
        amount:
          type: number
          description: Live-quoted checkout total for the anchored service, USD
        currency:
          type: string
          enum:
          - USD
          description: ISO currency, USD
        service:
          type: string
          description: The service the amount is anchored to
        handoff_url:
          type: string
          format: uri
          description: Opens the SMKlog checkout prefilled with this shipment
        identified_product_title:
          type: string
          description: What the estimator understood the item to be
        quote_reused:
          type: boolean
          description: True when the amount came from a quote_id you supplied, so no carrier call was spent
        note:
          type: string
          description: 'Standing caveats: live quote, human confirms consents and pays'
  securitySchemes:
    clientCredentials:
      type: oauth2
      description: 'Optional. Every operation works without a token. A client that wants its own hourly rate-limit bucket holds OAuth 2.0 client_credentials issued by hand (registration instructions at https://smklog.com/auth.md) and sends the opaque bearer it gets from /oauth/token. Discovery: /.well-known/oauth-authorization-server.'
      flows:
        clientCredentials:
          tokenUrl: https://quote-api.smklog.com/oauth/token
          scopes:
            quote: Price parcels and prepare checkouts from a dedicated per-client rate-limit bucket
externalDocs:
  description: 'Developer portal: docs, schemas, playground, rate limits, status'
  url: https://smklog.com/developers/
x-provenance:
  method: published
  publisher: SMKlog (SMKLOG-2022 LLC)
  source: https://quote-api.smklog.com/openapi.json
  published: '2026-10-12'
x-mcp:
  transport: streamable-http
  endpoint: https://quote-api.smklog.com/mcp
  serverCard: https://quote-api.smklog.com/.well-known/mcp/server-card.json