---
title: "Amortization Schedule Builder"
method: POST
path: "/v1/tools/build_amortization_schedule"
tags: ["TODO_TAGS_REVIEW", "TODO_AP2_EXPORT_REVIEW"]
---

# Amortization Schedule Builder

`POST /v1/tools/build_amortization_schedule`

## Request

- Base URL: `https://ainumbers.co`
- URL: `https://ainumbers.co/v1/tools/build_amortization_schedule`
- Auth: none declared

Deterministic amortization schedule builder covering level-payment, ARM (index plus margin, periodic and lifetime caps, recast), interest-only, balloon, and temporary buydown (2-1 or 3-2-1) structures, per the unit-period and odd-days conventions in 12 CFR 1026 Appendix J. Returns the full period-by-period schedule (principal, interest, ending balance), totals, a schedule_digest, and advances/payments arrays shaped for direct use as the actuarial APR solver's input. Cents-integer fixed-point math throughout; no floating-point drift.

**Tool URL:** https://ainumbers.co/chaingraph/art-332-build-amortization-schedule.html

## Request body

- object
  - `buydown_schedule` unknown[], required
    - unknown
  - `buydown_type` unknown, required
  - `io_periods` number
  - `lifetime_cap_pct` number: Percentage value
  - `lifetime_floor_pct` number: Percentage value
  - `loan_amount` number
  - `margin_pct` number: Percentage value
  - `nominal_amortization_periods` number, required
  - `note_rate_pct` number: Percentage value
  - `num_payments` number
  - `odd_days` number: Duration in days
  - `payment_amount` number
  - `periodic_cap_pct` number: Percentage value
  - `periods_per_year` number
  - `rate_changes` unknown[], required
    - unknown
  - `recast` boolean, required
  - `schedule_type` unknown, required
  - `unit_period_days` number: Duration in days

## Response `200`

Successful tool execution result

- object
  - `advances` object[]
    - `amount` integer
    - `periods_from_consummation` integer
  - `loan_amount` integer
  - `note` string
  - `note_rate_pct` integer
  - `num_payments` integer
  - `odd_days` integer
  - `payment_amount` number
  - `payments` object[]
    - `amount` number
    - `periods_from_consummation` integer
  - `periods_per_year` integer
  - `regulatory_basis` string
  - `schedule` object[]
    - `ending_balance` number
    - `interest` integer
    - `payment_amount` number
    - `period_index` integer
    - `periods_from_consummation` integer
    - `principal` number
  - `schedule_type` string
  - `totals` object
    - `ending_balance` integer
    - `num_payments` integer
    - `total_interest` number
    - `total_principal` integer
  - `unit_period_days` integer

---

[API](https://skmtc.dev/ainumbers/apis/ainumbers-co-fintech-intelligence-suite.md) · [All operations](https://skmtc.dev/ainumbers/apis/ainumbers-co-fintech-intelligence-suite/llms.txt) · [OpenAPI document](https://skmtc.dev/ainumbers/apis/ainumbers-co-fintech-intelligence-suite/revisions/b462e4f5bb28?raw)