> ## Documentation Index > Fetch the complete documentation index at: https://docs.decimal.ai/llms.txt > Use this file to discover all available pages before exploring further. # Start a Stripe Checkout session for a plan upgrade > Start a plan change and return the URL to send the browser to. Body: {"plan": "core" | "pro"} Returns: {"checkout_url": "..."} — a Stripe Checkout URL for an org with no live subscription, or the billing page for an org whose EXISTING subscription was modified in place. Changing the price on the live subscription is what keeps a plan change to one subscription: opening a second Checkout session for an org that already subscribes would leave it billed for both plans at once. The response shape is identical either way, so clients keep doing `location = checkout_url`. 400 carries the reason when we refuse the change — already on that plan, a downgrade (use the portal), or a custom subscription. ## OpenAPI ````yaml /openapi.json post /api/v1/billing/checkout openapi: 3.1.0 info: title: DecimalAI Platform description: Agent Dataset Lifecycle Platform — Backend API version: 0.1.0 servers: - url: https://api.decimal.ai description: Production security: - BearerAuth: [] tags: - name: traces description: >- Ingest, search, and inspect agent execution traces. A trace is the atomic unit of the platform — every other feature (evaluation, compatibility scoring, dataset building) operates on traces. Each trace is auto-tagged with the manifest hash of the agent that produced it. - name: eval-scores description: >- Push, fetch, and aggregate per-trace evaluation scores. Scores carry source provenance (built-in, DeepEval, LangSmith, custom) and feed the unified decision engine, which produces a keep / repair / replay / drop verdict per trace. - name: skills description: >- Manage reusable instruction blocks (SKILL.md files) that modify agent behavior. Skills are first-class manifest components — changes to a skill appear in your regression-check impact reports. Use these endpoints to create, version, fork, and sync skills with your local SKILL.md files. - name: manifests description: >- Register and inspect manifest versions. A manifest is a snapshot of your agent's structural identity (tools, prompts, models, skills) at a point in time. The SDK registers manifests automatically; these endpoints expose the underlying records. - name: datasets description: >- Build versioned SFT/DPO training datasets from manifest-classified, eval-scored traces. Datasets are reproducible — each version locks the manifest and filter set used to build it. Export as JSONL, Parquet, or push to HuggingFace Hub. - name: replay description: >- Re-execute historical traces against a new manifest version. Replay is the deferred-future capability for behavioral verification of agent changes. The SDK creates a replay batch, your worker executes each task, then submits results back here for eval scoring. - name: registry description: >- Browse and install published skills from the public skills registry. Each registry skill carries a SkillScore — an evidence-tiered quality composite computed from real-world evals, benchmarks, and ratings across organizations. Installing creates a fork in your org — edits don't affect the public version. - name: agents description: >- List and inspect agents, plus their multi-agent topology (orchestrator → sub-agent edges discovered from traces). Agents are identified by a stable agent_name string set in your SDK init() call. - name: import description: >- Bulk-import historical traces from another observability platform or a JSONL backup. Useful for migrating from LangSmith / Braintrust / Langfuse. Duplicate trace IDs are silently skipped — re-running an import is safe. paths: /api/v1/billing/checkout: post: tags: - billing summary: Start a Stripe Checkout session for a plan upgrade description: >- Start a plan change and return the URL to send the browser to. Body: {"plan": "core" | "pro"} Returns: {"checkout_url": "..."} — a Stripe Checkout URL for an org with no live subscription, or the billing page for an org whose EXISTING subscription was modified in place. Changing the price on the live subscription is what keeps a plan change to one subscription: opening a second Checkout session for an org that already subscribes would leave it billed for both plans at once. The response shape is identical either way, so clients keep doing `location = checkout_url`. 400 carries the reason when we refuse the change — already on that plan, a downgrade (use the portal), or a custom subscription. operationId: create_checkout_api_v1_billing_checkout_post parameters: - name: Authorization in: header required: false schema: type: string title: Authorization - name: decimal_session in: cookie required: false schema: anyOf: - type: string - type: 'null' title: Decimal Session requestBody: required: true content: application/json: schema: type: object additionalProperties: true title: Payload responses: '200': description: Successful Response content: application/json: schema: {} '422': description: Validation Error content: application/json: schema: $ref: '#/components/schemas/HTTPValidationError' components: schemas: HTTPValidationError: properties: detail: items: $ref: '#/components/schemas/ValidationError' type: array title: Detail type: object title: HTTPValidationError ValidationError: properties: loc: items: anyOf: - type: string - type: integer type: array title: Location msg: type: string title: Message type: type: string title: Error Type input: title: Input ctx: type: object title: Context type: object required: - loc - msg - type title: ValidationError securitySchemes: BearerAuth: type: http scheme: bearer description: Enter your API key (e.g. dai_sk_test_key_001) ````