RealVest Real Estate MCP Server

export class AffordabilityCalculator { getSchema() { return { type: 'object', properties: { annual_income: { type: 'number', description: 'Annual gross income in dollars', minimum: 0 }, monthly_debts: { type: 'number', description: 'Total monthly debt payments (car, credit cards, student loans, etc.)', minimum: 0 }, down_payment: { type: 'number', description: 'Down payment amount in dollars', minimum: 0 }, interest_rate: { type: 'number', description: 'Annual interest rate as a percentage (e.g., 7.5 for 7.5%)', minimum: 0, maximum: 20 }, property_tax_rate: { type: 'number', description: 'Annual property tax rate as percentage of home value (default: 1.2%)', default: 1.2 }, insurance_rate: { type: 'number', description: 'Annual insurance rate as percentage of home value (default: 0.5%)', default: 0.5 }, hoa_monthly: { type: 'number', description: 'Monthly HOA fees (default: 0)', default: 0 }, loan_term_years: { type: 'number', description: 'Loan term in years (default: 30)', default: 30 } }, required: ['annual_income', 'monthly_debts', 'down_payment', 'interest_rate'] }; } calculate(params) { const { annual_income, monthly_debts, down_payment, interest_rate, property_tax_rate = 1.2, insurance_rate = 0.5, hoa_monthly = 0, loan_term_years = 30 } = params; // Calculate monthly income const monthlyIncome = annual_income / 12; // DTI limits const frontEndRatio = 0.28; // 28% for housing const backEndRatio = 0.36; // 36% total debt // Calculate maximum monthly payment based on DTI ratios const maxHousingPayment = monthlyIncome * frontEndRatio; const maxTotalDebtPayment = monthlyIncome * backEndRatio; const maxPaymentAfterDebts = maxTotalDebtPayment - monthly_debts; // Use the lower of the two limits const maxMonthlyPayment = Math.min(maxHousingPayment, maxPaymentAfterDebts); // Calculate loan amount based on payment const monthlyRate = interest_rate / 100 / 12; const numPayments = loan_term_years * 12; // Account for property tax, insurance, and HOA const propertyTaxMonthly = (property_tax_rate / 100) / 12; const insuranceMonthly = (insurance_rate / 100) / 12; // Calculate maximum principal and interest payment const maxPrincipalInterest = maxMonthlyPayment - hoa_monthly; // Solve for loan amount using mortgage formula let maxLoanAmount; if (monthlyRate === 0) { maxLoanAmount = maxPrincipalInterest * numPayments; } else { // Account for property tax and insurance in the calculation // These are based on home value, so we need to solve iteratively let homePrice = 200000; // Initial guess let iterations = 0; while (iterations < 20) { const taxAndInsurance = homePrice * (propertyTaxMonthly + insuranceMonthly); const availableForPrincipalInterest = maxMonthlyPayment - taxAndInsurance - hoa_monthly; const newLoanAmount = availableForPrincipalInterest * ((1 - Math.pow(1 + monthlyRate, -numPayments)) / monthlyRate); const newHomePrice = newLoanAmount + down_payment; if (Math.abs(newHomePrice - homePrice) < 100) break; homePrice = newHomePrice; iterations++; } maxLoanAmount = homePrice - down_payment; } let maxHomePrice = maxLoanAmount + down_payment; // Calculate down payment percentage let downPaymentPercent = (down_payment / maxHomePrice) * 100; // Check if PMI is required (less than 20% down) const pmiRequired = downPaymentPercent < 20; const pmiMonthly = pmiRequired ? maxLoanAmount * 0.005 : 0; // 0.5% annually // Recalculate if PMI is required if (pmiRequired) { const availableAfterPMI = maxMonthlyPayment - pmiMonthly; const taxAndInsurance = maxHomePrice * (propertyTaxMonthly + insuranceMonthly); const availableForPrincipalInterest = availableAfterPMI - taxAndInsurance - hoa_monthly; maxLoanAmount = availableForPrincipalInterest * ((1 - Math.pow(1 + monthlyRate, -numPayments)) / monthlyRate); maxHomePrice = maxLoanAmount + down_payment; downPaymentPercent = (down_payment / maxHomePrice) * 100; } // Calculate actual monthly payment breakdown const principalInterest = maxLoanAmount * (monthlyRate * Math.pow(1 + monthlyRate, numPayments)) / (Math.pow(1 + monthlyRate, numPayments) - 1); const propertyTax = maxHomePrice * propertyTaxMonthly; const insurance = maxHomePrice * insuranceMonthly; const totalMonthlyPayment = principalInterest + propertyTax + insurance + pmiMonthly + hoa_monthly; // Calculate ratios const frontEndActual = (totalMonthlyPayment / monthlyIncome) * 100; const backEndActual = ((totalMonthlyPayment + monthly_debts) / monthlyIncome) * 100; return { max_home_price: Math.round(maxHomePrice), max_loan_amount: Math.round(maxLoanAmount), down_payment: down_payment, down_payment_percent: downPaymentPercent.toFixed(1), monthly_payment_breakdown: { principal_interest: Math.round(principalInterest), property_tax: Math.round(propertyTax), insurance: Math.round(insurance), pmi: Math.round(pmiMonthly), hoa: hoa_monthly, total: Math.round(totalMonthlyPayment) }, debt_to_income: { front_end_ratio: frontEndActual.toFixed(1), back_end_ratio: backEndActual.toFixed(1), front_end_limit: (frontEndRatio * 100).toFixed(0), back_end_limit: (backEndRatio * 100).toFixed(0) }, loan_details: { interest_rate: interest_rate, loan_term_years: loan_term_years, total_payments: numPayments, pmi_required: pmiRequired }, affordability_summary: { monthly_income: Math.round(monthlyIncome), max_housing_payment: Math.round(maxMonthlyPayment), current_monthly_debts: monthly_debts, remaining_for_housing: Math.round(maxMonthlyPayment) } }; } }