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Mortgage Calculator

Mortgage payment calculator — monthly payments, amortization schedules, and affordability estimates.

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status: healthy status status healthy healthy tools: 4 tools tools 4 4 type: calculator type type calculator calculator lifecycle: maintained lifecycle lifecycle maintained maintained Finance

Data source: Standard amortization formulas

REST Bridge Endpoint https://context.gnist.ai/rest/mortgage-calculator/
Authentication

All requests require a Gnist-API-Key header (or api_key query parameter).

Free tier: 100 calls/day. Get your API key.

Tools (4)

calculate_monthly_payment

Calculate fixed monthly mortgage payment.

Given a loan amount, interest rate, and term, computes the monthly payment,
total amount paid over the life of the loan, and total interest.

ParameterTypeRequiredDescription
principalnumberrequiredLoan amount.
annual_ratenumberrequiredAnnual interest rate as a percentage (e.g. 5.5 for 5.5%).
term_yearsintegerrequiredLoan term in years.
Request Body
{
  "principal": 1.0,
  "annual_rate": 1.0,
  "term_years": 1
}
calculate_amortization

Generate a full amortization schedule for a mortgage.

Returns monthly entries showing how each payment splits between principal
and interest, plus the remaining balance after each payment.

ParameterTypeRequiredDescription
principalnumberrequiredLoan amount.
annual_ratenumberrequiredAnnual interest rate as a percentage (e.g. 5.5 for 5.5%).
term_yearsintegerrequiredLoan term in years.
Request Body
{
  "principal": 1.0,
  "annual_rate": 1.0,
  "term_years": 1
}
calculate_affordability

Estimate how much home a buyer can afford.

Uses the 28% front-end DTI ratio: maximum housing payment is 28% of gross
monthly income, minus existing debts.

ParameterTypeRequiredDescription
annual_incomenumberrequiredGross annual income.
annual_ratenumberrequiredAnnual interest rate as a percentage (e.g. 5.5 for 5.5%).
monthly_debtsnumberoptionalExisting monthly debt obligations. (default: 0.0)
down_paymentnumberoptionalCash available for down payment. (default: 0.0)
term_yearsintegeroptionalLoan term in years. (default: 30)
Request Body
{
  "annual_income": 1.0,
  "annual_rate": 1.0
}
report_feedback

Report a bug, feature request, or general feedback for this data source.

Use this when something doesn't work as expected, when you'd like
a new feature, or when you have suggestions for improvement.

Args:
feedback: Describe the issue or suggestion.
feedback_type: One of 'bug', 'feature_request', or 'general'.

ParameterTypeRequiredDescription
feedbackstringrequired
feedback_typestringoptional (default: "general")
Request Body
{
  "feedback": "example"
}

Quick Start

Shell
curl -X POST "https://context.gnist.ai/rest/mortgage-calculator/calculate_monthly_payment" \
  -H "Content-Type: application/json" \
  -H "Gnist-API-Key: YOUR_API_KEY" \
  -d '{"principal": 1.0, "annual_rate": 1.0, "term_years": 1}'
Python
import httpx

resp = httpx.post(
    "https://context.gnist.ai/rest/mortgage-calculator/calculate_monthly_payment",
    headers={"Gnist-API-Key": "YOUR_API_KEY"},
    json={
  "principal": 1.0,
  "annual_rate": 1.0,
  "term_years": 1
},
)
print(resp.json())

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