Amortization Schedule

Row-by-row loan amortization schedules: monthly or daily accrual, extra principal, PMI, biweekly.

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What it can do

    What data it sees

    Do you need an account

    No: the server works without sign-in

    Row-by-row loan amortization schedules: monthly or daily accrual, extra principal, PMI, biweekly.

    How to connect

    How to connect Amortization Schedule to Claude

    The server address to paste into Claude settings:

    https://amortize.gumballtools.com/api/mcp

    1. Open Claude (claude.ai or the desktop app).
    2. Go to Settings → Connectors.
    3. Click Add custom connector.
    4. Paste the server address copied below into Remote MCP server URL and click Add.
    5. In a chat, click + → Connectors and switch the new connector on.

    Custom connectors are available on Free, Pro, Max, Team and Enterprise plans (Free is limited to one). On Team and Enterprise an organization Owner adds the connector first under Organization settings → Connectors.

    Authorization

    After you click Add, a sign-in window for the service opens. Sign in with your own account and approve access. Claude never sees your password.

    How to connect Amortization Schedule to ChatGPT

    The server address to paste into ChatGPT settings:

    https://amortize.gumballtools.com/api/mcp

    1. Open ChatGPT in a browser (chatgpt.com). A Plus, Pro, Business, Enterprise or Edu plan is required.
    2. Turn on developer mode once: Settings → Apps → Advanced settings → Developer mode.
    3. Open Settings → Connectors and click Create.
    4. Fill in the form: Name (anything), Description (one line about what the service does), MCP server URL (copy it below).
    5. Under Authentication choose OAuth if the service requires sign-in, otherwise None. Click Create.
    6. In a new chat open + → Apps/Connectors and enable the connector.

    OpenAI has renamed this section before (Connectors → Apps/Plugins). If the label differs, search settings for "developer mode". On Business/Enterprise workspaces an admin must allow custom connectors first.

    Authorization

    On first use ChatGPT opens the service's sign-in window. Sign in and approve access.

    How to connect Amortization Schedule to Cursor

    The server address to paste into Cursor settings:

    https://amortize.gumballtools.com/api/mcp

    Fastest: click Open in Cursor below and confirm the prompt.

    Manually:

    1. In Cursor open Settings → Cursor Settings → MCP and click Add new global MCP server.
    2. Paste the JSON copied below into ~/.cursor/mcp.json (per project: .cursor/mcp.json in the repo root).
    3. Save the file. The server appears in the MCP list; authorize it there if asked.

    Authorization

    If the service needs sign-in, an authorize button appears next to the server in the MCP list.

    Server tool list (1)

    Raw names from tools/list. Only developers need these.

    amortizeBuilds the full row-by-row amortization schedule for a loan — interest, principal, PMI, and running balance for every payment — instead of just the monthly payment amount. Use this whenever a row-by-row schedule matters: "what is my balance after payment 47", "what does an extra $200/month do to my payoff date", "when does PMI drop off", or "give me the whole amortization table". Do not do this arithmetic by hand or in your head. Two things go wrong reliably when a model tries: 1. THE LAST ROW. The textbook payment formula only amortizes to exactly zero in infinite precision. Rounded to cents and carried over up to a few hundred rows, a hand-rolled schedule drifts and ends with a balance of a few cents to a few dollars instead of zero — exactly the row a person checks against their real statement. This tool recomputes the final row as "remaining balance + that row's interest" so it always ends at zero, and reports the delta. 2. COMPOUNDING CONVENTION. Fixed mortgages compound monthly (rate/12). HELOCs, most auto loans, and most private student loans accrue interest DAILY on the actual number of days between payments, which is a genuinely different schedule, not a rounding variant. Guessing the wrong one silently produces a plausible but wrong table. Input: `principal`, `annualRatePercent` (e.g. 6.5), `termMonths` (integer), and `compounding` ("monthly" or "daily") are required. For `compounding: "daily"`, supply EITHER `startDate` (YYYY-MM-DD — the tool derives real day counts and leap years from the calendar itself) OR `dayCountBasis` ("30/360" | "actual/365" | "actual/actual") for a hypothetical loan with no dates — never both are needed, and supplying neither is refused rather than guessed. Optional: `paymentFrequency` ("monthly" default | "biweekly", which requires daily compounding — pass `paymentOverride` if the actual billed payment differs from the textbook one, e.g. a HELOC's quoted minimum; `extraPrincipal` as `{type:"oneOff",amount,atPaymentNumber}` or