curl -X POST https://fanalyx.com/v1/api/analysis/amortization \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "principal": 300000,
    "annualRate": 0.045,
    "years": 30,
    "startDate": "2025-01-01"
  }'

const response = await fetch('https://fanalyx.com/v1/api/analysis/amortization', {
  method: 'POST',
  headers: {
    'Authorization': 'Bearer YOUR_API_KEY',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    principal: 300000,
    annualRate: 0.045,
    years: 30,
    startDate: '2025-01-01'
  })
});

const data = await response.json();
console.log(data);

import requests

response = requests.post(
    'https://fanalyx.com/v1/api/analysis/amortization',
    headers={
        'Authorization': 'Bearer YOUR_API_KEY',
        'Content-Type': 'application/json'
    },
    json={
        'principal': 300000,
        'annualRate': 0.045,
        'years': 30,
        'startDate': '2025-01-01'
    }
)

data = response.json()
print(data)

import type { AmortizationInput, AmortizationResult } from '@fanalyx/sdk';

const input: AmortizationInput = {
  principal: 300000,
  annualRate: 0.045,
  years: 30,
  startDate: '2025-01-01'
};

const response = await fetch('https://fanalyx.com/v1/api/analysis/amortization', {
  method: 'POST',
  headers: {
    'Authorization': `Bearer ${process.env.FANALYX_API_KEY}`,
    'Content-Type': 'application/json'
  },
  body: JSON.stringify(input)
});

const result: AmortizationResult = await response.json();

3. Try the Interactive Playground

Test endpoints directly in your browser without an API key:

Open API Playground

4. Explore the API

View interactive documentation and try all endpoints:

View OpenAPI Documentation →

API Tiers

Free

$0/month

✓ 1,000 requests/month
✓ All calculation endpoints
✓ Basic support
✓ OpenAPI documentation

Perfect for testing and small projects

Popular

Pro

$49/month

✓ 50,000 requests/month
✓ All calculation endpoints
✓ Priority support
✓ Higher rate limits
✓ Usage analytics

For production applications

Enterprise

Custom

✓ Unlimited requests
✓ Custom endpoints
✓ Dedicated support
✓ SLA guarantee
✓ White-label options

For large-scale deployments

Available Endpoints

Loan Amortization

POST /v1/api/analysis/amortization

Calculate loan amortization schedules with principal, interest, and balance breakdowns.

View Example

{
  "principal": 300000,
  "annualRate": 0.045,
  "years": 30,
  "startDate": "2025-01-01"
}

Lease Analysis

POST /v1/api/analysis/lease

Analyze lease vs buy decisions with NPV, IRR, and cashflow projections.

View Example

{
  "assetCost": 50000,
  "monthlyLease": 1200,
  "leaseTerm": 36,
  "residualValue": 20000,
  "discountRate": 0.05
}

EBITDA Forecasting

POST /v1/api/analysis/ebitda

Generate financial forecasts with revenue, expenses, and EBITDA projections.

Plus 6 More Models

• Savings Goal Calculator
• Auto Loan Analysis
• Retirement Planning
• Budget Optimization
• Debt Payoff Strategy
• Student Loan Analysis

View all endpoints in API docs →

Why Use Our API?

⚡

Edge Deployed

Running on Cloudflare's global network for ultra-low latency from anywhere in the world.

🔒

Secure & Tested

All calculations are deterministic, unit tested, and validated against golden test cases.

📊

Fully Documented

Complete OpenAPI specification with interactive examples and TypeScript types.

🎯

Type-Safe

Strict input validation with Zod schemas and detailed error messages.

Authentication

All API requests require authentication using your API key in the Authorization header:

Authorization: Bearer YOUR_API_KEY

Security Note: Never expose your API key in client-side code. Always make API requests from your backend server.

Rate Limits

All requests include rate limit headers:

X-RateLimit-Limit: 1000
X-RateLimit-Remaining: 999
X-RateLimit-Reset: 1735689600

Tier	Requests/Month	Requests/Second
Free	1,000	1
Pro	50,000	10
Enterprise	Unlimited	Custom

Error Reference

All errors follow a consistent format with actionable error codes:

{ "error": "INVALID_INPUT", "message": "Principal must be a positive number",
          "code": 400, "field": "principal", "docs": "https://fanalyx.com/docs/errors/INVALID_INPUT"
          }

400 - INVALID_INPUT

Cause: Request body doesn't match schema (missing fields, wrong types, invalid values)

Solution: Check the `field` property and ensure your input matches the endpoint requirements

Common examples: negative principal, invalid date format, missing required field

401 - UNAUTHORIZED

Cause: Missing or invalid API key

Solution: Include `Authorization: Bearer YOUR_API_KEY` header with valid key

Check your API key at /dashboard or generate a new one

429 - RATE_LIMIT_EXCEEDED

Cause: Too many requests in time window

Solution: Check `X-RateLimit-Reset` header and retry after that timestamp

Consider upgrading to Pro tier for higher limits

500 - INTERNAL_ERROR

Cause: Unexpected server error

Solution: Retry with exponential backoff. If persists, contact support

Include the `X-Request-ID` header value when reporting issues

SDKs & Client Libraries

Official SDKs provide type-safe wrappers and handle authentication automatically:

TypeScript/JavaScript

npm install @fanalyx/sdk

import Fanalyx from '@fanalyx/sdk';

const client = new Fanalyx({
  apiKey: process.env.FANALYX_API_KEY
});

const result = await client.amortization({
  principal: 300000,
  annualRate: 0.045,
  years: 30
});

View on GitHub →

Python

pip install fanalyx

from fanalyx import Fanalyx

client = Fanalyx(
    api_key=os.environ['FANALYX_API_KEY']
)

result = client.amortization(
    principal=300000,
    annual_rate=0.045,
    years=30
)

View on GitHub →

Generate your own: Download our OpenAPI spec and use OpenAPI Generator to create clients in Go, Ruby, PHP, and more.

Webhooks

Receive real-time notifications for events like calculations completing or quota warnings:

Available Events

calculation.completed Fired when an async calculation finishes
quota.warning Fired at 80% quota usage
quota.exceeded Fired when quota limit is reached

Webhook Signature Verification

const crypto = require('crypto');

function verifyWebhook(payload, signature, secret) {
  const hash = crypto
    .createHmac('sha256', secret)
    .update(payload)
    .digest('hex');
  
  return hash === signature;
}

// In your webhook handler
const isValid = verifyWebhook(
  req.body,
  req.headers['x-fanalyx-signature'],
  process.env.WEBHOOK_SECRET
);

if (!isValid) {
  return res.status(401).send('Invalid signature');
}

Performance Optimization

🚀 Use HTTP/2

All endpoints support HTTP/2 multiplexing. Make parallel requests over a single connection for better performance.

💾 Cache Responses

Calculation results are deterministic. Cache them by input hash to avoid redundant requests.

ETag: "abc123"
Cache-Control: public, max-age=31536000

🔄 Batch Requests

For multiple calculations, use batch endpoints (coming soon) or make concurrent requests.

🗜️ Enable Compression

Include `Accept-Encoding: gzip` header to reduce response size by ~70%.

Use Cases & Tutorials

🏠 Build a Mortgage Calculator

Create a full-featured mortgage calculator with amortization schedules, payment breakdowns, and affordability analysis.

Read tutorial →

Financial Planning Dashboard

Build a comprehensive financial planning app with retirement projections, savings goals, and debt payoff strategies.

Read tutorial →

Auto Loan Comparison Tool

Help users compare financing options with side-by-side loan analysis and total cost calculations.

Read tutorial →

Testing Sandbox

Use test API keys for development and CI/CD without consuming your quota:

Test API Key

test_sk_1234567890abcdef

Test keys return mock data and don't count toward rate limits. Perfect for unit tests and CI/CD pipelines.

Example Test Response

{
  "test": true,
  "payment": 1520.06,
  "totalInterest": 247221.60,
  "schedule": [/* mock data */]
}

API Changelog

v1.2.0 2025-10-22

✨ Added webhook support for async calculations
✨ New `/v1/api/analysis/budget` endpoint
🐛 Fixed rounding issues in amortization schedule

v1.1.0 2025-10-01

✨ Added EBITDA forecasting endpoint
⚡ Improved response times by 40%
📚 Enhanced OpenAPI documentation

v1.0.0 2025-09-15

Initial API release
9 financial calculation endpoints
OpenAPI specification

View full changelog →

Pricing Calculator

Estimate your monthly costs based on expected usage:

Expected monthly requests:

0 5,000 100k

$0/month

Recommended: Free Tier

Community & Support

💬

Security & Compliance

🔒 Data Security

• All data encrypted in transit (TLS 1.3)
• No calculation data stored after response
• API keys hashed with bcrypt
• Regular security audits

✅ Compliance

• GDPR compliant
• CCPA compliant
• SOC 2 Type II (in progress)
• PCI DSS compliant infrastructure

📜 Data Retention

We retain metadata (timestamps, request counts) for 90 days. Calculation inputs and results are not logged or stored.

🛡️ Best Practices

• Rotate API keys quarterly
• Use environment variables
• Implement request signing
• Monitor for anomalies

🔔 Status Updates

Check API health and uptime at /status

📊 Usage Dashboard

Monitor your API usage, quotas, and analytics

Ready to Get Started?

Get Your Free API Key

Developer API

Try the new Project Think-powered Fanalyx Agent

API Keys

Pricing

Dashboard

Quick Start

1. Get Your API Key

2. Make Your First Request

3. Try the Interactive Playground

4. Explore the API

API Tiers

Free

Pro

Enterprise

Available Endpoints

Loan Amortization

Lease Analysis

EBITDA Forecasting

Plus 6 More Models

Why Use Our API?

Edge Deployed

Secure & Tested

Fully Documented

Type-Safe

Authentication

Rate Limits

Error Reference

SDKs & Client Libraries

TypeScript/JavaScript

Python

Webhooks

Available Events

Webhook Signature Verification

Performance Optimization

🚀 Use HTTP/2

💾 Cache Responses

🔄 Batch Requests

🗜️ Enable Compression

Use Cases & Tutorials

🏠 Build a Mortgage Calculator

Financial Planning Dashboard

Auto Loan Comparison Tool

Testing Sandbox

Test API Key

Example Test Response

API Changelog

Pricing Calculator

Community & Support

Discord Community

GitHub Discussions

User Showcase

Security & Compliance

🔒 Data Security

✅ Compliance

📜 Data Retention

🛡️ Best Practices

Support & Resources

📖 API Documentation

📥 Download OpenAPI Spec

💻 GitHub Repository

📧 Email Support

🔔 Status Updates

📊 Usage Dashboard

Ready to Get Started?