> ## Documentation Index > Fetch the complete documentation index at: https://docs.lerian.studio/llms.txt > Use this file to discover all available pages before exploring further. # Preview amortisation schedule > Computes a deterministic declining-balance schedule for the supplied loan parameters and records it as the offer, returning the identifier that names it. Re-running an identical preview returns the same identifier and records no second offer. ## OpenAPI ````yaml /pt/openapi/v3-current/lender.yaml post /api/v1/loan-applications/preview-schedule openapi: 3.1.0 info: contact: email: contact@lerian.studio name: Lerian Studio url: https://lerian.studio description: >- Code-first OpenAPI 3.1 surface for the Lender service. Routes that move money are at-most-once per X-Idempotency: when one answers 5xx, the X-Idempotency-Fenced response header says whether that key is now refusing resends (true) or free to retry (false or absent). license: name: Lerian Studio General License title: Lender API version: 1.0.0 servers: - url: https://lender.sandbox.lerian.net security: - BearerAuth: [] tags: - description: >- Caller session projection: validated subject and effective permissions for the presented token. name: Session - description: >- Ledger accounting operations: journal entries and accrual postings for loan accounts. name: Accounting - description: >- Loan application intake and lifecycle: submission, decisioning, and status. name: LoanApplications - description: >- Loan product catalog: definition, versioning, and activation of lending products. name: LoanProducts - description: >- Loan account servicing operations: balances, schedules, and account-level actions. name: Loan Accounts - description: >- Portfolio dashboard read operations: aggregated portfolio and performance views. name: Dashboard - description: >- Jurisdiction registry: supported jurisdiction profiles and their capabilities. name: Jurisdictions - description: >- Jurisdiction-specific loan application operations (Brazil origination surface). name: Loan Applications - description: >- Tax computation operations for jurisdiction-specific lending (e.g. Brazil IOF). name: Tax - description: >- Brazil consignado privado operations: contract lifecycle, exclusion repair, and compensating adjustments. name: Consignado - description: >- Credit-instrument document template registry: versioned drafting and publication of CCB clausulado. name: DocumentTemplates paths: /api/v1/loan-applications/preview-schedule: post: tags: - LoanApplications summary: Preview amortisation schedule description: >- Computes a deterministic declining-balance schedule for the supplied loan parameters and records it as the offer, returning the identifier that names it. Re-running an identical preview returns the same identifier and records no second offer. operationId: previewLoanSchedule requestBody: content: application/json: schema: $ref: '#/components/schemas/SchedulePreviewHumaRequest' required: true responses: '200': content: application/json: schema: $ref: '#/components/schemas/SchedulePreviewHumaBody' description: OK '401': content: application/problem+json: schema: $ref: '#/components/schemas/Detail' description: Unauthorized '403': content: application/problem+json: schema: $ref: '#/components/schemas/Detail' description: Forbidden '422': content: application/problem+json: schema: $ref: '#/components/schemas/Detail' description: Unprocessable Entity '500': content: application/problem+json: schema: $ref: '#/components/schemas/Detail' description: Internal Server Error '503': content: application/problem+json: schema: $ref: '#/components/schemas/Detail' description: Service Unavailable default: content: application/problem+json: schema: $ref: '#/components/schemas/Detail' description: Error components: schemas: SchedulePreviewHumaRequest: additionalProperties: false properties: annualInterestRate: description: Annual interest rate as a decimal string (e.g. "0.12000000"). examples: - '0.12000000' type: string dayCountConvention: description: Day count convention identifier. examples: - ACT/365 type: string firstDueDate: description: >- Day the first instalment falls due (RFC3339 or YYYY-MM-DD). Omit it and the first instalment falls one month after the start date, clamped to the month's last day, which is the ordinary grid. Supply it and it becomes the grid: every later instalment falls on that day of the month, clamped to each month's last day so a ladder anchored on the 31st falls on the 30th in April and never spills into May, and the first period runs from the start date to this day — longer or shorter than a month, and charged by its real days. Naming the day the ordinary grid was going to fall on anyway is the same as omitting it, and prices the same ladder; naming any other day re-anchors the whole ladder on it, so two requests one day apart can move the SECOND instalment by more than one day. Refused when it is worth zero or fewer days from the start date by this day-count convention, when its first period would cost the whole instalment in interest so the first payment repays no principal, or when gracePeriodDays is also set. examples: - '2026-03-10' type: string gracePeriodDays: description: >- Grace period in days: the first instalment falls this many days after the start date instead of one month. Mutually exclusive with firstDueDate, which says the same thing by naming the day; sending both is refused. examples: - 30 format: int64 maximum: 365 minimum: 0 type: integer jurisdictionCode: description: ISO-2 jurisdiction code. examples: - BR maxLength: 2 minLength: 2 type: string loanProductVersionId: description: >- Loan product version whose admitted first-due-date window this preview should be bounded by. Optional: omit it and the preview prices whatever the arithmetic allows, which is what a quote made before a product is picked needs. Supply it together with firstDueDate and the preview answers the same refusal booking will, rather than quoting a ladder the door will not take. examples: - 018f4e4e-7a3f-7c2e-9a1b-2c3d4e5f6071 format: uuid type: string principalAmount: description: Principal amount as a decimal string (e.g. "50000.00"). examples: - '50000.00' type: string startDate: description: Schedule start date (RFC3339 or YYYY-MM-DD). examples: - '2026-06-14T00:00:00Z' type: string termMonths: description: Number of months. examples: - 24 format: int64 maximum: 600 minimum: 1 type: integer required: - principalAmount - annualInterestRate - termMonths - dayCountConvention - jurisdictionCode - startDate type: object SchedulePreviewHumaBody: additionalProperties: false properties: calendarReference: description: Identifier of the business calendar used to resolve due dates. type: string dayCountConvention: description: Day count convention applied to interest accrual. examples: - ACT/365 type: string effectiveCostPreview: $ref: '#/components/schemas/SchedulePreviewHumaEffectiveCost' description: >- Effective-cost breakdown; present only when the jurisdiction profile computes one. installments: description: Ordered amortisation schedule, one entry per installment. items: $ref: '#/components/schemas/SchedulePreviewHumaInstallmentLine' type: - array - 'null' jurisdictionCode: description: ISO-2 jurisdiction code resolved for this preview. examples: - BR type: string jurisdictionExtensions: $ref: '#/components/schemas/SchedulePreviewHumaJurisdictionExtensions' description: >- Per-jurisdiction overlay payload; present only when the profile emits one. profileVersion: description: Jurisdiction profile version used to compute the schedule. examples: - 1.0.0 type: string scheduleOfferSnapshotId: description: >- Identifier of the offer this preview recorded; derived from the frozen inputs, so an identical preview returns the same value. Absent whenever no offer was recorded — the request carries no tenant identity, the offer store was unavailable, or the service is misconfigured — and the schedule is returned in every one of those cases. examples: - 6f2b9a41-0c3d-5e7f-9a12-4b8c6d0e1f37 type: string totalInterest: description: >- Sum of interest across all installments as a decimal string, minor-unit precision scale 2 (e.g. "4321.00"). examples: - '4321.00' type: string totalPrincipal: description: >- Sum of principal across all installments as a decimal string, minor-unit precision scale 2 (e.g. "50000.00"). examples: - '50000.00' type: string required: - installments - totalInterest - totalPrincipal - jurisdictionCode - profileVersion - dayCountConvention - calendarReference type: object Detail: additionalProperties: true properties: code: description: >- Stable, machine-readable domain error code scoped to the emitting service (format: -NNNN). type: string detail: description: >- A human-readable explanation specific to this occurrence of the problem. examples: - Property foo is required but is missing. type: string errors: description: Optional list of individual error details items: $ref: '#/components/schemas/ErrorDetail' type: - array - 'null' instance: description: >- A URI reference that identifies the specific occurrence of the problem. examples: - https://example.com/error-log/abc123 format: uri type: string status: description: HTTP status code examples: - 400 format: int64 type: integer title: description: >- A short, human-readable summary of the problem type. This value should not change between occurrences of the error. examples: - Bad Request type: string type: default: about:blank description: A URI reference to human-readable documentation for the error. examples: - https://example.com/errors/example format: uri type: string upstream: $ref: '#/components/schemas/Upstream' description: >- RFC 9457 extension member: the error a proxied third-party provider reported. Absent unless the emitting service explicitly surfaced one. type: object SchedulePreviewHumaEffectiveCost: additionalProperties: false properties: effectiveCostAnnualPct: description: >- Effective annual cost as a decimal-string percentage, scale 8 (e.g. "12.00000000"). examples: - '12.00000000' type: string effectiveCostMonthlyPct: description: >- Effective monthly cost as a decimal-string percentage, scale 8 (e.g. "0.94888100"). examples: - '0.94888100' type: string memoryOfCalculation: additionalProperties: {} description: >- Opaque step-by-step record of the effective-cost calculation (audit trail). type: object methodId: description: >- Identifier of the effective-cost calculation method applied by the jurisdiction profile. type: string rateTableSnapshot: additionalProperties: {} description: Opaque snapshot of the rate table inputs used in the calculation. type: object required: - methodId - effectiveCostAnnualPct - effectiveCostMonthlyPct - rateTableSnapshot - memoryOfCalculation type: object SchedulePreviewHumaInstallmentLine: additionalProperties: false properties: dueDate: description: Installment due date (date-only, YYYY-MM-DD). examples: - '2026-06-14' type: string interestAmount: description: >- Interest portion of the installment as a decimal string, minor-unit precision scale 2 (e.g. "234.56"). examples: - '234.56' type: string number: description: 1-based installment sequence number. examples: - 1 format: int64 type: integer principalAmount: description: >- Principal portion of the installment as a decimal string, minor-unit precision scale 2 (e.g. "1000.00"). examples: - '1000.00' type: string remainingBalance: description: >- Outstanding principal balance after this installment as a decimal string, minor-unit precision scale 2 (e.g. "49000.00"). examples: - '49000.00' type: string totalAmount: description: >- Total installment amount (principal + interest) as a decimal string, minor-unit precision scale 2 (e.g. "1234.56"). examples: - '1234.56' type: string required: - number - dueDate - totalAmount - principalAmount - interestAmount - remainingBalance type: object SchedulePreviewHumaJurisdictionExtensions: additionalProperties: false properties: body: additionalProperties: {} description: >- Opaque per-jurisdiction overlay payload decoded from the use-case result. type: object overlayKey: description: >- Identifier of the jurisdiction overlay that produced this extension payload. type: string required: - overlayKey - body type: object ErrorDetail: additionalProperties: false properties: location: description: >- Where the error occurred, e.g. 'body.items[3].tags' or 'path.thing-id' type: string message: description: Error message text type: string value: description: The value at the given location type: object Upstream: additionalProperties: false properties: code: description: The upstream provider's own error code, verbatim. examples: - E4001 type: string message: description: >- The upstream provider's own error message, verbatim (bounded, never its raw response body). examples: - account not found at provider type: string type: object securitySchemes: BearerAuth: bearerFormat: JWT description: JWT bearer token issued by the identity provider. scheme: bearer type: http ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.