Contacts: The Foundation of Intelligent Messaging

Contacts in Sent represent a fundamental shift in how messaging platforms approach multi-channel communication.

Rather than forcing developers to manage the complexity of different messaging channels, contacts provide a unified abstraction that handles channel intelligence, validation, and routing automatically.

Contacts Architecture

The Sent Contacts Architecture is designed to be intelligent and flexible, while allowing you to have full control over the messaging experience.

Channel-Agnostic Abstraction

Traditional messaging platforms require developers to understand and integrate with separate APIs for SMS, WhatsApp, and other channels. This leads to several problems such as integration complexity, validation overhead, routing decisions, and fallback handling, all of which need to be implemented manually.

Sent solves all of the above by providing a channel-agnostic abstraction. When you send a message to a contact, the platform handles all channel-specific complexity behind a unified interface.

The Contact as a Validated Communication Endpoint

A contact in Sent is fundamentally different from a simple phone number or user record. It represents:

A validated, intelligent communication endpoint that:

• Knows which messaging channels can successfully reach the recipient
• Understands the optimal channel for delivery based on regional preferences and availability
• Maintains channel-specific formatting and validation rules
• Provides automatic fallback routing when primary channels fail

This abstraction allows developers to focus on their application logic rather than the intricacies of multi-channel messaging infrastructure.

The Routing Decision Engine

Sent's contact architecture implements sophisticated routing logic that considers multiple factors:

Channel Availability Hierarchy:

Routing Factors

Persistent State

Contacts maintain persistent state that benefits future interactions:

• Channel availability is cached and periodically refreshed
• Routing decisions improve based on delivery history
• Validation status prevents repeated failed delivery attempts

This persistence means that applications naturally become more efficient over time without additional developer effort.

Phone Number Normalization

Contacts handle the complexity of phone number formatting across different contexts:

• E.164 format: International standard for programmatic use
• International format: Human-readable international representation
• National format: Localized formatting for user interfaces
• RFC format: Standardized format for system integration

This multi-format support ensures that contacts work correctly regardless of how phone numbers are provided or displayed in your application.

Customer Scoping and Isolation

Contacts are scoped to individual customers, providing:

• Access control: Customers can only access their own contacts
• Billing isolation: Message costs are attributed correctly
• Data privacy: Contact information remains segregated between customers

This architecture supports multi-tenant applications while maintaining security and billing accuracy.

Channel-Specific Metadata

While contacts abstract channel complexity, they also preserve channel-specific information when needed:

• WhatsApp profile status: Whether a number has an active WhatsApp Business API registration
• SMS carrier information: Network-specific delivery capabilities
• Regional restrictions: Compliance and availability constraints by geography

This metadata enables advanced applications to make informed decisions while still benefiting from the unified API approach.

Contact Intelligence

Automatic Contact Creation

Contacts follow a lazy creation pattern that reduces integration friction. This approach means developers never need to pre-register contacts. The system creates and optimizes them automatically during the first messaging interaction.

Here's how it works:

Real-Time Channel Validation

When a contact is created, Sent performs real-time validation against all supported channels:

This validation ensures that every contact represents a deliverable endpoint, reducing bounce rates and failed message attempts.

Contact Enrichment Over Time

Contacts become more intelligent through usage:

• Delivery success patterns inform future routing decisions
• Channel preferences are learned from recipient engagement
• Validation status is periodically refreshed to maintain accuracy

This creates a feedback loop where messaging performance improves automatically as the system learns more about each contact.

Contacts for Developers

Sent supports two primary patterns for working with contacts. Both patterns leverage the same underlying intelligence but offer different levels of control and visibility.

❌ Traditional approach:

if (user.hasWhatsApp) {
    sendWhatsApp(message, user.phone);
} else {
    sendSMS(message, user.phone);
}

✅ Contact-based approach:

sendMessage(message, contact);