> ## Documentation Index > Fetch the complete documentation index at: https://docs.trycactus.com/llms.txt > Use this file to discover all available pages before exploring further. # What-if on a finished report > Recalculates the saved model with changed assumptions and returns the headline figures before and after. Nothing is saved or charged. ## OpenAPI ````yaml /api-reference/openapi.yaml post /v1/underwritings/{underwriting_id}/previews openapi: 3.1.0 info: title: Cactus Partner API version: 1.0.0-draft.1 summary: Document extraction and automated underwriting for CRE. description: | # Overview The Cactus Partner API provides two products: - **Extraction** — upload commercial real estate documents (offering memoranda, rent rolls, T-12 / operating statements, and other business documents) and receive structured, validated JSON with per-field confidence. - **Underwriting** — provide a property address, asset class, and notification email (documents optional) to run a full automated underwriting; results are delivered as a hosted financial-analysis report link plus a machine-readable summary. ## Authentication Every request carries an API key: `Authorization: Bearer ck_live_...` (or `ck_sandbox_...`). Keys are issued by Cactus at kickoff and can be rotated or revoked at any time. ## Products and access Accounts are enabled per product, so not every endpoint below is available to every account: | Product | Endpoints | | --- | --- | | Extraction | `/v1/extractions` | | Underwriting | `/v1/underwritings` | | Usage reporting | `/v1/usage` | `/v1/documents` and `/v1/webhook-endpoints` are available to every account — uploads and webhook delivery underpin both products. Calling an endpoint your account is not enabled for returns `403` with code `product_not_enabled`; contact api@trycactus.com to add a product. A `403` with code `missing_scope` means the account *is* enabled but this particular key was issued without that scope — use a key that carries it. The MCP server advertises only the tools your key can use, so the same rules apply there. ## Sandbox `ck_sandbox_` keys hit the same endpoints but never debit your usage pool: uploads are accepted, and jobs return deterministic fixture output within seconds. Use sandbox keys for integration development and CI. Registering a sandbox document under a documented example filename (e.g. `example-rent-roll-1.xlsx`) returns the real extracted output of that reference document — see the Sandbox guide for the full list. ## Asynchronous jobs Extractions and underwritings are asynchronous. Create the job (`202 Accepted`), then either poll the job resource or register a webhook endpoint to receive signed events (recommended). Typical extraction turnaround is minutes. ## Billing semantics A document is **accepted** when it passes validation (size caps, page/row counts, type resolution). Acceptance debits your usage pool at the fixed rate-card price for the document type — before processing, so pricing is deterministic. Rejected documents are never charged. Documents exceeding their type's size cap bill as multiple units of the same type; the accept response discloses `billed.units`. Files over 500 pages or 100 MB are rejected outright. ## Idempotency All `POST` endpoints accept an `Idempotency-Key` header (any unique string, e.g. a UUID). Retrying a request with the same key returns the original response instead of creating a duplicate. ## Errors Errors follow RFC 9457 (`application/problem+json`) and always include a stable machine-readable `code` and the `request_id` to quote in support requests. ## Versioning The path major version (`/v1`) changes only for breaking API changes. Extraction output schemas are versioned independently per document type (e.g. `rent_roll.v1`) and declared in every result; breaking output changes ship as a new schema version with advance notice and an overlap window. --- All field-level output schemas — `RentRollData` (`rent_roll.v1`), `T12Data` (`t12.v1`), `OfferingMemorandumData` (`offering_memorandum.v1`), and `GenericDocumentData` (`facts.v1`) — are finalized against the extraction engine's real output. contact: name: Cactus API Support email: api@trycactus.com license: name: Proprietary — Cactus API License Agreement identifier: LicenseRef-Cactus-Partner-Agreement servers: - url: https://api.trycactus.com description: Production (live and sandbox keys) security: - apiKey: [] tags: - name: Documents description: Upload and manage documents via presigned URLs. - name: Extractions description: Structured data extraction jobs and results. - name: Underwritings description: Automated underwriting runs. - name: Usage description: Usage pool balance and metered activity. - name: Webhook Endpoints description: Manage endpoints that receive signed event notifications. paths: /v1/underwritings/{underwriting_id}/previews: parameters: - $ref: '#/components/parameters/UnderwritingId' - $ref: '#/components/parameters/EndUser' post: tags: - Underwritings summary: What-if on a finished report description: | Recalculates the saved model with changed assumptions and returns the headline figures before and after. Nothing is saved or charged. operationId: previewUnderwritingChange requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/UnderwritingPreviewRequest' responses: '200': description: The preview. content: application/json: schema: $ref: '#/components/schemas/UnderwritingPreview' '400': $ref: '#/components/responses/BadRequest' '403': $ref: '#/components/responses/Forbidden' '404': $ref: '#/components/responses/NotFound' '409': description: The underwriting has not completed. content: application/problem+json: schema: $ref: '#/components/schemas/Problem' '422': description: An assumption is unknown or not editable, or the value is invalid. content: application/problem+json: schema: $ref: '#/components/schemas/Problem' '503': description: The calculation service is temporarily unavailable. content: application/problem+json: schema: $ref: '#/components/schemas/Problem' components: parameters: UnderwritingId: name: underwriting_id in: path required: true schema: type: string example: uw_01J9ZK3M EndUser: name: X-Cactus-End-User in: header required: false schema: type: string maxLength: 255 description: | Act for one of your end users (the `end_user_ref` you pass when creating underwritings). Limits every underwriting, document and extraction call to that user's resources. Required on MCP connections once your account serves end users. schemas: UnderwritingPreviewRequest: type: object required: - changes additionalProperties: false properties: changes: type: array minItems: 1 maxItems: 50 items: $ref: '#/components/schemas/AssumptionChange' UnderwritingPreview: type: object required: - object - underwriting_id - saved - changes - before - after properties: object: type: string const: underwriting_preview underwriting_id: type: string saved: type: boolean const: false changes: type: array items: type: object properties: assumption_id: type: string label: type: string previous_value: {} value: {} option_id: type: string before: type: object description: Headline figures of the saved report. after: type: object description: The same figures with the changes. derived_changes: type: array description: >- Assumptions the model changed on its own because of the requested ones (e.g. a lease-up valuation switch). `assumption_id` is null for a model setting that isn't in the assumptions list. items: type: object properties: assumption_id: type: string nullable: true label: type: string previous_value: {} value: {} disclosure: type: string description: Why the model made the derived changes. Problem: type: object description: RFC 9457 problem details. required: - title - status - code - request_id properties: type: type: string format: uri description: > Link to this code's entry on the errors page. An anchor, not a path — every code lives on the one page. example: https://docs.trycactus.com/errors#document_over_size_cap title: type: string example: Document exceeds the size limit status: type: integer example: 422 detail: type: string example: Files over 500 pages or 100 MB are rejected and not charged. code: type: string description: Stable machine-readable error code. example: document_over_size_cap request_id: type: string errors: type: array description: Field-level validation errors, when applicable. items: type: object properties: field: type: string code: type: string message: type: string AssumptionChange: type: object required: - assumption_id additionalProperties: false description: Exactly one of `value` or `option_id`. properties: assumption_id: type: string value: oneOf: - type: number - type: string maxLength: 200 - type: boolean option_id: type: string responses: BadRequest: description: Malformed request. content: application/problem+json: schema: $ref: '#/components/schemas/Problem' Forbidden: description: > The key authenticated, but this product is not available to it. `product_not_enabled` — your account has not been enabled for this product; contact api@trycactus.com. `missing_scope` — your account has the product but this particular key was issued without it; use a key that carries the scope. content: application/problem+json: schema: $ref: '#/components/schemas/Problem' examples: product_not_enabled: summary: Account not enabled for the product value: type: https://docs.trycactus.com/errors#product_not_enabled title: Product not enabled for this account status: 403 detail: >- Your account is not enabled for underwriting. Contact api@trycactus.com to enable it. code: product_not_enabled request_id: req_01J9Z6X2QK8N4M missing_scope: summary: Key narrower than the account value: type: https://docs.trycactus.com/errors#missing_scope title: API key lacks the required scope status: 403 detail: >- This API key does not have the 'underwriting' scope. Use a key with underwriting access. code: missing_scope request_id: req_01J9Z6X2QK8N4M NotFound: description: Resource does not exist (or belongs to another partner). content: application/problem+json: schema: $ref: '#/components/schemas/Problem' securitySchemes: apiKey: type: http scheme: bearer bearerFormat: ck_live_* or ck_sandbox_* description: Partner API key issued by Cactus. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.