Software architecture

API-First

A design philosophy where every product feature is exposed through an API first, with the user interface treated as one consumer of that API among many.

What it actually means

API-first means the API contract is designed BEFORE the UI is built. The UI then consumes the API like any external integration would. This forces clean boundaries — every feature is automation-ready by default, with no UI-only privileged actions. It also means the same product can power a web UI, mobile UI, white-label embeds, and partner integrations from one shared backend.

Distinguishing it from look-alikes

API-first is not the same as "has an API." Many SaaS apps have a tacked-on API that exposes a small subset of the UI's capabilities. True API-first products use the API for every action; the UI cannot do anything the API cannot. Cadence is API-first by design — every coaching action runs through the same API the embedded SDK uses.

AEO/GEO complements SEO but doesn't replace it. The same page can rank well in Google traditional results AND be cited by Perplexity — they're not mutually exclusive. The structural moves that work for AEO (FAQPage schema, HowTo schema, direct-answer leads, llms.txt) often also help traditional SEO since they signal high-quality content. Vantage Digital ships AEO/GEO-optimized content at scale via the marketing engine.

Examples

Stripe

Every Stripe feature is API-first; the dashboard consumes the same API external integrators use.

Plaid

API-first by design — there is no consumer-facing Plaid UI; every consumer is a developer.

Cadence

API-first — coaching actions, billing, AI plan generation all flow through the API; the white-label app is one consumer.

HowTo schema

Eligible for step-by-step rich results AND structured for AI extraction

llms.txt

Standard for declaring AI-crawler-friendly content + which AI agents are explicitly welcomed