123456import { saas } from '@fourbyfour/sdk'; const fbf = saas({  apiKey: process.env.FOURBYFOUR_API_KEY,  projectId: process.env.FOURBYFOUR_PROJECT_ID});

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Get your API key from the dashboard. Each vertical gives you typed events and pre-built workflows optimized for your industry.

Quick Start

Two functions. That's all you need.

Select your vertical

fbf.track()

→ triggers Payment Recovery workflow

123456789// Payment failed → triggers recovery workflowawait fbf.track('payment.failed', {  userId: 'u_123',  amount: 99,  currency: 'USD',  plan: 'Pro',  subscriptionId: 'sub_456',  billingCycle: 'monthly'});

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fbf.notify()

→ helps us optimize delivery

1234567// Send context to help optimize deliveryawait fbf.notify({  userId: 'u_123',  timezone: 'America/New_York',  preferredChannel: 'email',  tier: 'premium'});

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What happens next?

When you call track('payment.failed'), our Payment Recovery workflow kicks in automatically. We handle timing, channel selection, message optimization, all tuned from patterns across thousands of companies.

AI Integration Generator

Answer a few questions about your stack and we'll generate a step-by-step integration guide that you can feed to your AI coding assistant (Claude Code, Cursor, Copilot, etc.).

What's your tech stack?

We'll generate code examples in your language.

How to use the generated guide:

Complete the wizard above to generate your integration guide
Copy the guide or download as a markdown file
Open your AI coding assistant (Claude Code, Cursor, etc.)
Paste the guide and ask it to "implement this integration"
Replace YOUR_PROJECT_ID and YOUR_API_KEY with your actual values from the dashboard
Review the changes and commit

Two Functions

Two functions. No PII. That's the entire SDK.

Select your vertical

fbf.track(event, payload)

Events that trigger workflows

1234567891011121314151617181920212223import { saas } from '@fourbyfour/sdk'; const fbf = saas({  apiKey: process.env.FOURBYFOUR_API_KEY,  projectId: process.env.FOURBYFOUR_PROJECT_ID}); // Minimum: just userId (we use defaults)await fbf.track('payment.failed', {  userId: 'u_123'}); // Full: everything you know (better optimization)await fbf.track('payment.failed', {  userId: 'u_123',  amount: 99,  currency: 'USD',  plan: 'Pro',  subscriptionId: 'sub_456',  billingCycle: 'monthly',  failureReason: 'card_declined',  attemptNumber: 1});

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fbf.notify(context)

Context that helps us optimize

12345678910// Send context anytime to help us optimize deliveryawait fbf.notify({  userId: 'u_123',  timezone: 'Asia/Kolkata',      // When to reach them  tier: 'premium',               // Priority signals  preferredChannel: 'whatsapp',  // Channel preference  language: 'en',                // Localization  ltv: 500,                      // Value signals  converted: true                // Feedback after conversion});

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Data Philosophy

Minimum (just userId)

Works out of the box. We use intelligent defaults optimized across thousands of companies.

123await fbf.track('payment.failed', {  userId: 'u_123'});

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Full (everything you know)

Better optimization. More context = smarter timing, channels, and messaging.

123456await fbf.track('payment.failed', {  userId: 'u_123',  amount: 99,  plan: 'Pro',  // ... everything helps});

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The key: Send what you have, when you have it. No need to block on missing fields. We fill gaps with smart defaults, then improve as you send more.

What Goes Where

trackNo PII

Business events: amount, plan, cartTotal

notifyNo PII

User context: timezone, tier, preferences

resolverTransient

Delivery info: email, phone, name

Function	Data Type	Example	PII?
`track`	Business events	amount, plan, cartTotal	No
`notify`	User context	timezone, tier, preferences	No
`resolver`	Delivery info	email, phone, name	Yes (transient)

Notice: PII only flows through your resolver endpoint, fetched just-in-time, used for delivery, never stored. See the Resolver section.

Resolver

Just-in-time PII. Your data stays in your system until the moment of delivery.

How It Works

Workflow triggers

User event matches a workflow

We call your resolver

Request only needed fields

You return PII

Email, phone, name: what's needed

We deliver & discard

Used for send, never stored

Request & Response

We send:

{}JSON

1234567891011POST /api/fourbyfour/resolveHeaders:  x-fbf-signature: sha256=... Body:{  "userId": "u_123",  "fields": ["email", "name"],  "workflowId": "payment-recovery",  "channel": "email"}

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You respond:

{}JSON

123456789101112HTTP 200 OK {  "email": "user@example.com",  "name": "John"} // Or if user not found:HTTP 404 Not Found{  "error": "User not found"}

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Implementation

12345678910111213141516171819202122232425// Express / Next.js API routeapp.post('/api/fourbyfour/resolve', async(req, res) => {  // Verify the request is from Fourbyfour  const signature = req.headers['x-fbf-signature'];  if(!verifySignature(signature, req.body, process.env.FBF_WEBHOOK_SECRET)) {    return res.status(401).json({ error: 'Invalid signature' });  }   const { userId, fields, workflowId, channel } = req.body;   // Fetch user from your database  const user = await db.users.findById(userId);  if(!user) {    return res.status(404).json({ error: 'User not found' });  }   // Return only requested fields  const response: Record<string, string> = {};   if(fields.includes('email')) response.email = user.email;  if(fields.includes('name')) response.name = user.firstName;  if(fields.includes('phone')) response.phone = user.phone;   res.json(response);});

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Fields by Channel

email+ name

SMS

phone+ name

Push

pushToken+ name, device

Channel	Required	Optional
Email	`email`	`name`
SMS	`phone`	`name`
WhatsApp	`phone`	`name`
Push	`pushToken`	`name`, `device`

Why This Architecture

Privacy by Design

• PII never leaves your system until needed
• We request only what the channel requires
• Data used for delivery, then discarded

Always Fresh

• No stale emails or phones
• User updates their info? Next send has it
• User deletes account? Returns 404, we skip

You Stay in Control

• Return only what you want to share
• Add business logic (block certain users)
• GDPR compliant by default

Workflows

63 pre-built workflows optimized across thousands of companies. Just track the event. We handle timing, channels, and messaging.

SaaS: Convert trials based on how they're using the product

How it works

Track event

Call fbf.track()

Workflow triggers

Matches your event

We optimize

Timing, channel, message

Revenue recovered

Payments, trials, users

View all SaaS events and examples

Channels

We deliver via the optimal channel. You just provide the resolver endpoint. We handle the rest.

Email

Best for: detailed info, rich content

email

SMS

Best for: urgent, time-sensitive

phone

Best for: conversational, global

phone

Push

Best for: real-time, mobile

pushToken

How We Select Channels

User Preference

If you sent preferredChannel via notify(), we start there.

Context Analysis

We consider timezone, urgency, past engagement, and message type.

Cross-org Learning

We know "users in this segment convert 2x better via WhatsApp".

What We Optimize

Timing→ Send at 10am local

User's timezone is IST

Channel→ Use SMS over email

Past engagement higher on SMS

Frequency→ Wait before next

User received message yesterday

Urgency→ Escalate to SMS

Payment fails in 24h

Signal	Example	Impact
Timing	User's timezone is IST	Send at 10am local time
Channel	Past engagement higher on SMS	Use SMS over email
Frequency	User received message yesterday	Wait before next touch
Urgency	Payment fails in 24h	Escalate to SMS

Automatic Fallbacks

If a channel fails or isn't available, we automatically try the next best option:

Email fails→Try SMS→Try Push

123456789// Payment failed → triggers recovery workflowawait fbf.track('payment.failed', { userId: 'u_123', amount: 99, currency: 'USD', plan: 'Pro', subscriptionId: 'sub_456', billingCycle: 'monthly'});

1234567891011121314151617181920212223import { saas } from '@fourbyfour/sdk'; const fbf = saas({ apiKey: process.env.FOURBYFOUR_API_KEY, projectId: process.env.FOURBYFOUR_PROJECT_ID}); // Minimum: just userId (we use defaults)await fbf.track('payment.failed', { userId: 'u_123'}); // Full: everything you know (better optimization)await fbf.track('payment.failed', { userId: 'u_123', amount: 99, currency: 'USD', plan: 'Pro', subscriptionId: 'sub_456', billingCycle: 'monthly', failureReason: 'card_declined', attemptNumber: 1});

12345678910// Send context anytime to help us optimize deliveryawait fbf.notify({ userId: 'u_123', timezone: 'Asia/Kolkata', // When to reach them tier: 'premium', // Priority signals preferredChannel: 'whatsapp', // Channel preference language: 'en', // Localization ltv: 500, // Value signals converted: true // Feedback after conversion});

Function

Data Type

Example

PII?

track

Business events

amount, plan, cartTotal

notify

User context

timezone, tier, preferences

resolver

Delivery info

email, phone, name

Yes (transient)

12345678910111213141516171819202122232425// Express / Next.js API routeapp.post('/api/fourbyfour/resolve', async(req, res) => { // Verify the request is from Fourbyfour const signature = req.headers['x-fbf-signature']; if(!verifySignature(signature, req.body, process.env.FBF_WEBHOOK_SECRET)) { return res.status(401).json({ error: 'Invalid signature' }); } const { userId, fields, workflowId, channel } = req.body; // Fetch user from your database const user = await db.users.findById(userId); if(!user) { return res.status(404).json({ error: 'User not found' }); } // Return only requested fields const response: Record<string, string> = {}; if(fields.includes('email')) response.email = user.email; if(fields.includes('name')) response.name = user.firstName; if(fields.includes('phone')) response.phone = user.phone; res.json(response);});

Channel

Required

Optional

email

name

SMS

phone

name

phone

name

Push

pushToken

name, device

Signal

Example

Impact

Timing

User's timezone is IST

Send at 10am local time

Channel

Past engagement higher on SMS

Use SMS over email

Frequency

User received message yesterday

Wait before next touch

Urgency

Payment fails in 24h

Escalate to SMS