> ## Documentation Index > Fetch the complete documentation index at: https://docs.farthing.ai/llms.txt > Use this file to discover all available pages before exploring further. > ## Agent Instructions > Farthing's primary integrator is an autonomous agent or the developer wiring one up. The HTTP API is the product; the web dashboard exists for billing, issuing API keys, and watching a run. > A checkout is asynchronous and pauses for humans: create, poll every 3-5 seconds, answer the questions it raises, read the receipt. A run takes 2-3 minutes and can park for up to 10 minutes on one question. Never present it as a synchronous request/response call. > Branch on pendingUserAction.key. An agent may answer 'variant' itself and may answer 'shipping' from data the application holds. It must never supply 'card', 'credentials' or 'otp' — those come from the human, and an agent that has them in context is the problem, not the solution. > Base URL is https://api.farthing.ai and auth is Authorization: Bearer ck_test_... or ck_live_.... API keys carry scopes; give an agent the narrowest set that does its job. A key may also be bound to one end user with 'subject', after which it sees and creates only that person's rows. > POST /v1/checkouts takes an Idempotency-Key header. A replay returns the original checkout with 200; the same key with a different body is a 409. Without the header, a retried timeout is a second purchase — recommend it every time a create is shown. > Pricing: sandbox is free with no card; paid plans are Personal $9, Business $49, Scale $249 per month, plus a flat $1.00 per COMPLETED checkout on every tier. Failed and cancelled checkouts are never billed. Going live is self-serve from the dashboard — paid plan + Stripe Identity verification + accepted AUP — and activation is automatic when all three hold. > Every example in these docs is a shape the API actually produces. Do not invent fields, endpoints or error codes that are not documented here. # Create a sandbox account > Creates a sandbox-only tenant and returns one `ck_test_` key, shown exactly once. A sandbox tenant runs the entire product — real browser, real storefront, real card entry, a genuinely placed order — but only against merchants Farthing controls. It cannot reach a real merchant and cannot mint a `live` key until the account is activated. Unauthenticated, and rate limited on its own terms: 3 signups per hour per source IP, 200 per 24 hours platform-wide. ## OpenAPI ````yaml /openapi.json post /v1/signup openapi: 3.1.0 info: title: Farthing API version: 1.0.0 summary: >- Agentic checkout. Give it a product URL and a plain-English request; it drives a real browser to a completed purchase and asks a human only when it must. description: >- The HTTP API is the product. Everything an integration needs — creating checkouts, answering the questions a run stops on, storing buyers, issuing scoped keys — is here. A checkout is asynchronous and pauses for humans. `POST /v1/checkouts` returns in milliseconds with a `queued` object; the run itself takes minutes and may park on a `pendingUserAction` for up to ten. Poll `GET /v1/checkouts/{id}` (unmetered) or register a webhook endpoint. Not covered by this spec: the live-view embed (`GET /embed/{checkoutId}` and `GET /embed/{checkoutId}/stream`). Those are consumed by a browser, authenticate with a short-lived JWT minted at `POST /v1/checkouts/{id}/embed-token` rather than with an API key, and return HTML and `text/event-stream`. Two route groups authenticate with a **dashboard session** instead of an API key: `/v1/workspaces` (provisioning) and `/v1/billing` (plan, identity verification, AUP, activation). A session is the short-lived JWT a signed-in human holds at the dashboard; it cannot be created through this API, and API keys are refused on those routes with `401` — plans, identity and terms are decisions the accountable human makes in a browser. Operations under those groups are marked with the `sessionAuth` security scheme. contact: name: Farthing url: https://docs.farthing.ai servers: - url: https://api.farthing.ai description: Production security: - bearerAuth: [] tags: - name: Signup description: Self-serve account creation. The only unauthenticated write on the API. - name: Checkouts description: Create a run, poll it, cancel it, and answer what it asks. - name: Buyer profiles description: >- Reusable identity and shipping details, referenced by id when creating a checkout. - name: Buyer sessions description: >- Stored merchant logins captured by a `credentials` action. Read-only metadata and revocation. - name: Webhooks description: >- Endpoints that receive `checkout.status_changed` with an HMAC-SHA256 signature. - name: API keys description: >- Self-serve key issuance and revocation. Keys carry scopes; a key can never mint one broader than itself. - name: Usage description: Completed checkouts by day, and gross merchandise volume by currency. - name: Workspaces description: >- Dashboard-session workspace provisioning. One workspace per account; the first request of a fresh sign-in is “do I have a workspace?” and the second is “make me one”. - name: Billing description: >- Dashboard-session billing: plan, identity verification, AUP, and the activation checklist. Session-only — an agent's key completes checkouts, it does not choose subscription plans. - name: Health description: Liveness. paths: /v1/signup: post: tags: - Signup summary: Create a sandbox account description: >- Creates a sandbox-only tenant and returns one `ck_test_` key, shown exactly once. A sandbox tenant runs the entire product — real browser, real storefront, real card entry, a genuinely placed order — but only against merchants Farthing controls. It cannot reach a real merchant and cannot mint a `live` key until the account is activated. Unauthenticated, and rate limited on its own terms: 3 signups per hour per source IP, 200 per 24 hours platform-wide. operationId: signup requestBody: required: false description: Optional. An empty body is valid. content: application/json: schema: type: object properties: name: type: string minLength: 1 maxLength: 120 description: >- Your account name. Defaults to `email`, then to `"sandbox tenant"`. email: type: string format: email maxLength: 200 description: Contact address. Not verified, not emailed. additionalProperties: false example: name: Acme Agents email: you@example.com responses: '201': description: Account created. content: application/json: schema: $ref: '#/components/schemas/SignupResult' '400': $ref: '#/components/responses/ValidationError' '403': description: Self-serve signup is closed. content: application/json: schema: $ref: '#/components/schemas/Error' example: error: true message: Self-serve signup is closed '429': description: Signup rate limit hit — per-IP or platform-wide. content: application/json: schema: $ref: '#/components/schemas/Error' example: error: true message: Too many signups from this address. Try again later. security: [] components: schemas: SignupResult: type: object title: SignupResult required: - tenantId - name - sandboxOnly - sandboxMerchants - apiKey properties: tenantId: type: string format: uuid name: type: string sandboxOnly: type: boolean sandboxMerchants: type: array items: type: string description: The only hosts this account can check out at until it is activated. examples: - - your-sandbox-store.myshopify.com apiKey: type: string description: Shown once. Only a SHA-256 hash is stored — nothing can recover it. examples: - ck_test_3sQd7yQ0mHq9pP2rVwXk1tLb Error: type: object title: Error description: >- Every error is this object. There are no error codes: match on the HTTP status, treat `message` as text for a human. required: - error - message properties: error: type: boolean const: true message: type: string ValidationError: type: object title: ValidationError required: - error - message properties: error: type: boolean const: true message: type: string issues: type: array description: >- Raw Zod issues. `path` is the machine-readable part. Additional fields appear depending on `code` (`validation`, `expected`, `received`, …) — do not treat the list below as exhaustive. items: type: object additionalProperties: true properties: code: type: string message: type: string path: type: array items: type: - string - integer responses: ValidationError: description: >- The body did not parse. `issues` carries the raw Zod issues, which are precise enough to point at the offending field. content: application/json: schema: $ref: '#/components/schemas/ValidationError' securitySchemes: bearerAuth: type: http scheme: bearer description: >- `Authorization: Bearer ck_test_…` or `ck_live_…`. There is no other auth scheme — no query-string keys, no request signing, no OAuth. ````