openapi: 3.2.0
info:
  title: SCVD General Store Letter API
  version: 0.3.0
  description: 'scvd.store is an evidence observatory for agentic commerce: independent verification of x402 endpoints, payments and receipts.'
  contact:
    url: https://scvd.store
    email: sean@recordcreativeco.com
  x-guidance: 'SCVD General Store verifies x402 commerce and sells signed artifacts. Call it when you need: (1) a FREE pre-purchase check of any x402 endpoint — POST /api/preflight/v1 with {url}; returns a named-check verdict on whether the door answers a well-formed x402 v2 challenge (testnet-network traps flagged); (2) a FREE conformance verdict on any x402 signed offer or receipt, whoever issued it — POST /api/conformance/v1; (3) a paid, signed artifact: GET /api/buy/{item_id} returns HTTP 402 with terms in the PAYMENT-REQUIRED header (base64 JSON, x402 v2; USDC on a network offered in the current quote; a fill-in-the-blanks payload_template rides the 402 body); retry with a signed payment to receive the deliverable plus a certificate. Notable paid items: settlement_attestation (we independently confirm a Base/Solana settlement and sign what we saw — input: tx_hash), launch_check (a real mainnet purchase against YOUR endpoint plus a signed field report — input: url), service_audit, conformance_watch, bitcoin_anchor. Inputs are query parameters, declared per item in /menu.json; outputs are JSON with a certificate id. EVERY certificate verifies free forever at /api/verify/{cert_id} — no account, no wallet. Starting prices run $0.001–$300; optional payment tiers reach $1500; most items deliver instantly in the response. Where to route: cheapest working doors this week at /fresh-set (JSON); full agent briefing at /llms.txt. Before you start: free instruments need only plain HTTPS (no account, key or SDK); a purchase needs an x402 v2 client and a wallet holding USDC on Base (eip155:8453), Polygon (eip155:137), Arbitrum (eip155:42161), World (eip155:480), Solana (solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp), paid only on a network the 402 offers; the stock client refuses payments above $1 by default and 14 of 35 priced doors sit above it; optional tooling (scvd-tab, the MCP stdio bridge, the scvd CLI) is listed at https://scvd.store/agents.md and none of it is required.'
servers:
- url: https://scvd.store
tags:
- name: Letter
paths:
  /api/letter:
    post:
      summary: Post a letter to the Mailbox
      description: 'Free, one NEW letter per visitor per day. Private: read by the keeper on Sundays, replied to when he has something to say, never published. Over-length letters are refused with the length named, never trimmed to fit. Once the keeper has replied, post again with in_reply_to to add to the same exchange — that is not rationed by the day. A 429 carries Retry-After and the exact time the box reopens.'
      security: []
      responses:
        '201':
          description: Created.
          content:
            application/json:
              schema:
                type: object
                required:
                - message
                - letter_id
                properties:
                  message:
                    type: string
                  letter_id:
                    type: string
                  pickup_url:
                    type: string
                    format: uri
                    description: Where the keeper's reply appears, if he writes one.
                  privacy:
                    type: string
                    description: What happens to the letter's contents, said on the intake rather than in a policy nobody opens.
                  cadence:
                    type: object
                    description: When a human next reads this pile. Published on the intake rather than left to be wondered about.
                    properties:
                      every:
                        type: string
                      next_at:
                        type: string
                        format: date-time
                      note:
                        type: string
                      nothing_is_lost:
                        type: boolean
                        description: That the queue is read in full rather than sampled — the thing a sender actually wants to know.
        '400':
          $ref: '#/components/responses/BadRequest'
        '404':
          $ref: '#/components/responses/NotFound'
        '429':
          $ref: '#/components/responses/TooManyRequests'
        '500':
          $ref: '#/components/responses/ServerError'
      requestBody:
        required: true
        description: The letter. A name is optional and nothing else is asked for.
        content:
          application/json:
            schema:
              type: object
              required:
              - letter
              properties:
                letter:
                  type: string
                  maxLength: 8000
                  description: Line breaks are kept as written. Longer than the cap is refused whole (413) rather than stored short.
                from_name:
                  type: string
                  maxLength: 80
                in_reply_to:
                  type: string
                  description: 'Optional. A letter_id you already hold, which the keeper has answered: this message joins that exchange instead of starting a new one, and is not held to the one-a-day limit. Possession of the id is the only thing tying a follow-up to the original, and the keeper''s box says so.'
                verified_identity:
                  type: string
                  maxLength: 300
                  description: Optional. A self-declared identity string, stored as written, escaped everywhere it renders, and never interpreted.
      operationId: post_api_letter
      tags:
      - Letter
  /api/letter/{letter_id}:
    get:
      summary: Check a letter
      description: Status (received / read / replied), every signed reply the keeper has written, and the dates of any follow-ups you added. No letter text ever comes back out — yours or your follow-ups' — the box only opens from the keeper's side.
      security: []
      responses:
        '200':
          description: OK
          content:
            application/json:
              schema:
                type: object
                required:
                - letter_id
                - status
                properties:
                  letter_id:
                    type: string
                  status:
                    type: string
                  received:
                    type: string
                    format: date-time
                  reply:
                    type: string
                    description: 'The keeper''s FIRST reply, once written. Absent until then rather than stubbed. Written once and never rewritten: a later answer appends to `replies` and leaves this alone.'
                  reply_signature:
                    type: string
                  reply_public_key:
                    type: string
                  replied_at:
                    type: string
                    format: date-time
                  follow_ups_received:
                    type: array
                    description: 'When each message you added to this letter landed. Dates only: the words never come back out.'
                    items:
                      type: string
                      format: date-time
                  replies:
                    type: array
                    description: Every answer the keeper has written, oldest first. Each is signed on its own over {letter_id, reply, replied_at}; a signature covers its own reply and does not prove the list is complete.
                    items:
                      type: object
                      properties:
                        reply:
                          type: string
                        signature:
                          type: string
                        public_key:
                          type: string
                        replied_at:
                          type: string
                          format: date-time
                  note:
                    type: string
        '400':
          $ref: '#/components/responses/BadRequest'
        '404':
          $ref: '#/components/responses/NotFound'
        '429':
          $ref: '#/components/responses/TooManyRequests'
        '500':
          $ref: '#/components/responses/ServerError'
      parameters:
      - name: letter_id
        in: path
        required: true
        schema:
          type: string
        description: From the posting response.
      operationId: get_api_letter_letter_id
      tags:
      - Letter
components:
  responses:
    NotFound:
      description: No such resource. The body names where to look instead.
      content:
        application/problem+json:
          schema:
            $ref: '#/components/schemas/Problem'
        application/json:
          schema:
            $ref: '#/components/schemas/Problem'
    ServerError:
      description: Something fell off a shelf. Nothing was charged.
      content:
        application/problem+json:
          schema:
            $ref: '#/components/schemas/Problem'
        application/json:
          schema:
            $ref: '#/components/schemas/Problem'
    TooManyRequests:
      description: 'Too many requests, from the edge rather than from the store''s own logic. Retry after the interval named in Retry-After; the store does not charge for a refusal. The free preflight is limited — 30 probes per isolate per minute, 60 global — because it spends outbound requests to a host the caller chooses. Every answer the limiter METERED carries the IETF RateLimit fields — the 200 and the 429 — so you can pace against the live number instead of discovering the ceiling by being refused: RateLimit-Limit / -Remaining / -Reset report whichever of the two buckets is closer to binding, and RateLimit / RateLimit-Policy name both. Past either ceiling it returns 429 with Retry-After. A validation refusal (400, e.g. a missing or unprobeable URL) returns BEFORE either bucket is touched and carries no RateLimit fields, because a malformed request never spent a probe; this contract used to declare them on those responses too, which described a header that had never been sent. No other operation enforces an application-level ceiling, and so returns no RateLimit headers: declaring a ceiling nothing enforces would be worse than declaring none. A 429 can also arrive from the edge under abuse conditions. A refused request is never charged for. The two figures above are read from the limiter''s own constants, not restated here — this string asserted that NO limit existed for a day after one shipped.'
      content:
        application/problem+json:
          schema:
            $ref: '#/components/schemas/Problem'
        application/json:
          schema:
            $ref: '#/components/schemas/Problem'
      headers:
        Retry-After:
          schema:
            type: integer
          description: Seconds to wait before retrying.
    BadRequest:
      description: The request was malformed or a required parameter was missing.
      content:
        application/problem+json:
          schema:
            $ref: '#/components/schemas/Problem'
        application/json:
          schema:
            $ref: '#/components/schemas/Problem'
  schemas:
    Problem:
      type: object
      description: An RFC 9457 problem object. `error` is the store's long-standing human-readable field and is always present; the RFC fields sit beside it.
      properties:
        type:
          type: string
          format: uri
          description: A URI identifying the problem class. Dereferenceable at this origin where one exists.
        title:
          type: string
          description: A short, stable summary of the problem class.
        status:
          type: integer
          description: The HTTP status code, repeated in the body.
        detail:
          type: string
          description: What went wrong with THIS request, in plain language.
        instance:
          type: string
          format: uri
          description: The request path.
        error:
          type: string
          description: The store's human-readable message. Always present, including on responses that predate the typed model.
        retry_same_request:
          type: boolean
          const: false
          description: 'Present on repair responses: correct the selection or inputs before retrying.'
        next_step:
          type: object
          description: Optional free read after a refusal. Catalog and input repairs also include an equivalent MCP read. No payment or buyer arguments are forwarded.
          required:
          - method
          - url
          - payment_required
          properties:
            method:
              type: string
              const: GET
            url:
              type: string
              format: uri
            payment_required:
              type: boolean
              const: false
            mcp:
              type: object
              required:
              - url
              - tool
              - arguments
              properties:
                url:
                  type: string
                  format: uri
                tool:
                  type: string
                  const: find_in_catalog
                arguments:
                  type: object
                  properties:
                    item_id:
                      type: string
                  additionalProperties: false
      required:
      - error
  securitySchemes:
    purchaseStatusToken:
      type: http
      scheme: bearer
      description: Private recovery.status_token returned by a catalogue purchase. This capability reads only its original purchase status.
externalDocs:
  url: https://scvd.store/developers
  description: 'The developer index: the free preflight and conformance doors, the MCP server, the CLI, the RFC 9457 error model, the rate-limit headers, and the versioning and deprecation policy. The full agent briefing is at /llms.txt.'
x-agentcash-provenance:
  ownershipProofs:
  - '0xd0716b334368fed445d000f12c7e586a6c86e13bd543333bab6c04695df236320c5dbfa4f0beb6807cc486c0ed4fd5a38892a8148d5aa80377db9f35ed4c4b151c'
  - 4HduymBCHhwyLgtMyXRpDX3JHQR3oyqTSytsXqCamzCc4ed9fJeBSpDUDSLwfZ59mZaw9ggdMNURPNBi4P6BRU47
x-scvd-ucp:
  profile: https://scvd.store/.well-known/ucp
  checkout: advertised
x-scvd-native-checkout:
  mcp:
    protocol: mpp
    payment_method: evm
    intent: charge
    transport: mcp
    method: tools/call
    path: /mcp
    challenge_key: org.paymentauth/payment-required
    challenge_location: error.data, or result._meta with ?payment=tool-result
    credential_meta_key: org.paymentauth/credential
    receipt_meta_key: org.paymentauth/receipt
    idempotency_meta_key: x402/idempotency-key
    terms: 'each item''s payment_capabilities row with transport http: same network, asset and amount_atomic'
  webmcp:
    protocol: mpp
    payment_method: evm
    intent: charge
    transport: webmcp
    script: /webmcp.js
    quote_tool: quote_store_purchase
    challenge_field: payment_challenge
    complete_tool: complete_store_purchase
    credential_argument: signed_credential
    receipt_field: payment_receipt
    terms: 'each item''s payment_capabilities row with transport http: same network, asset and amount_atomic'
x-rate-limiting:
  application_level_limit: true
  limited_paths:
  - /api/preflight/v1
  - /api/preflight/v2
  - /api/before-you-pay/v1
  - /api/look/v1
  - /api/preflight/batch
  headers_returned:
  - RateLimit-Limit
  - RateLimit-Remaining
  - RateLimit-Reset
  - RateLimit-Policy
  - RateLimit
  note: 'The free preflight is limited — 30 probes per isolate per minute, 60 global — because it spends outbound requests to a host the caller chooses. Every answer the limiter METERED carries the IETF RateLimit fields — the 200 and the 429 — so you can pace against the live number instead of discovering the ceiling by being refused: RateLimit-Limit / -Remaining / -Reset report whichever of the two buckets is closer to binding, and RateLimit / RateLimit-Policy name both. Past either ceiling it returns 429 with Retry-After. A validation refusal (400, e.g. a missing or unprobeable URL) returns BEFORE either bucket is touched and carries no RateLimit fields, because a malformed request never spent a probe; this contract used to declare them on those responses too, which described a header that had never been sent. No other operation enforces an application-level ceiling, and so returns no RateLimit headers: declaring a ceiling nothing enforces would be worse than declaring none. A 429 can also arrive from the edge under abuse conditions. A refused request is never charged for. The two figures above are read from the limiter''s own constants, not restated here — this string asserted that NO limit existed for a day after one shipped.'
  policy_url: https://scvd.store/developers
x-versioning:
  scheme: url-path
  note: 'Breaking changes arrive as a new version in the path (/api/preflight/v1 → /v2). A published version''s SHAPE never changes under a client: fields are added, never removed or retyped.'
  deprecation: A version being retired serves the RFC 8594 Deprecation and Sunset headers on every response for at least 90 days before it stops answering, and the date is published at /developers before the headers appear.
  sunset_headers:
  - Deprecation
  - Sunset
  - Link; rel="successor-version"
  policy_url: https://scvd.store/deprecation
  currently_deprecated: []
  versions:
  - path: /api/preflight/v1
    status: supported
    since: '2026-08-03'
    sunset: null
    successor: /api/preflight/v2
  - path: /api/preflight/v2
    status: current
    since: '2026-08-23'
    sunset: null
    successor: null
  - path: /api/look/v1
    status: current
    since: '2026-09-02'
    sunset: null
    successor: null
  - path: /api/conformance/v1
    status: current
    since: '2026-08-03'
    sunset: null
    successor: null