> ## Documentation Index > Fetch the complete documentation index at: https://docs.getmillwork.dev/llms.txt > Use this file to discover all available pages before exploring further. # Start checkout > Start a Stripe Checkout session for a credit top-up. ## OpenAPI ````yaml /openapi/solverapi.openapi.json post /v1/billing/checkout openapi: 3.1.0 info: description: >- Run approved AI models under data, cost, and time limits. A cost limit can stop another provider call after recorded spend reaches the limit; it cannot reverse a call already in progress. Each finished run returns a receipt naming the selected model and provider without including the prompt or model output. Use the model catalog for what your organization can run now. Provider secrets never appear in API requests or responses. Retry a mutation with the same Idempotency-Key and the same request body. title: Millwork API version: 1.0.0 servers: - url: https://api.getmillwork.dev security: [] tags: - description: >- Submit work, check its status, cancel it, and read the result. The API calls each run an execution. name: Runs - description: A record of how a run was handled, without prompt or result content. name: Receipts - description: Models this organization can use now. name: Models - description: Providers and sign-in methods that can be connected. name: Available providers - description: Provider accounts connected to this organization. name: Provider connections - description: >- One-time browser steps for connecting a provider without sending its secret in an API request. name: Secure credential setup - description: Exact models and provider routes available through connected accounts. name: Provider models - description: Create, label, list, and revoke organization API keys. name: API keys - description: Organization members and invitations. name: Members - description: Metered usage and quota state. name: Usage - description: Account, plan and allowance snapshot. name: Account - description: Checkout, billing portal and billing profile. name: Billing - description: Webhook endpoints, deliveries and replay. name: Webhooks - description: Organization-scoped compliance export. name: Compliance export - description: >- Models, agents, and skills Millwork can choose for a run. The API calls each one an arm. name: Registered options - description: >- Checks that score output and can stop, retry, or choose another option within the request policy. name: Output checks - description: Routing proposals and their review lifecycle. name: Repair proposals - description: Aggregate evaluation trend and repair history. name: Evaluation - description: Publisher and release identity records for supported models. name: Model definitions - description: >- Protected provider-credential references. Secret material never appears in this API. name: Credential references - description: Dashboard browser sign-in, sign-up, session lookup, and sign-out. name: Browser access - description: Read-only demo session setup. name: Demo - description: Machine setup and the authenticated organization profile. name: Organizations paths: /v1/billing/checkout: post: tags: - Billing summary: Start checkout description: Start a Stripe Checkout session for a credit top-up. operationId: postBillingCheckout requestBody: content: application/json: schema: additionalProperties: false properties: return_url: deprecated: true description: >- Deprecated. The server ignores this value and uses its configured application URL. minLength: 1 type: string topup_usd: minimum: 25 type: number required: - topup_usd type: object required: true responses: '201': content: application/json: schema: additionalProperties: false properties: checkout_url: description: Stripe-hosted Checkout page to redirect the browser to. format: uri type: string required: - checkout_url type: object description: Default Response 4XX: content: application/problem+json: schema: $ref: '#/components/schemas/Problem' description: >- Request failure in RFC 7807 format. The `type` field identifies the reason. Validation errors list affected fields. Rate and quota errors include `retry_after_s` and the `Retry-After` header. 5XX: content: application/problem+json: schema: $ref: '#/components/schemas/Problem' description: >- Server failure in RFC 7807 format. The response does not include internal error details. security: - bearerAuth: [] - sessionCookie: [] components: schemas: Problem: additionalProperties: false properties: detail: description: Short, safe, occurrence-specific description. Never a stack trace. type: string errors: description: Per-field validation failures (validation_failed only). items: additionalProperties: false properties: field: type: string message: type: string required: - field - message type: object type: array instance: description: Unique id for this occurrence, safe to quote in support requests. format: uuid type: string retry_after_s: description: >- Seconds to wait before retrying (rate_limited and quota_exceeded only; mirrored as the Retry-After header). type: integer status: description: HTTP status code, duplicated in the body per RFC 7807. type: integer title: description: Human-readable summary of the problem type. type: string type: description: Stable URI that identifies the error type. format: uri type: string required: - type - title - status - instance type: object securitySchemes: bearerAuth: description: Organization API key for application requests. scheme: bearer type: http sessionCookie: description: Dashboard browser session. Do not use this credential in an application. in: cookie name: solverapi_session type: apiKey ````