What is API Integration?
Definition: Connecting two or more software tools by making their APIs communicate with each other, enabling data flow and coordinated actions across the GTM stack.
API integration is how tools talk to each other. Every modern SaaS product exposes an API (Application Programming Interface) that lets external systems read and write data. When a GTM Engineer "integrates" Clay with HubSpot, they're configuring API calls that push enriched contact data from Clay into HubSpot records.
There are two ways to build integrations. Native integrations are built-in connections between tools: Clay has a HubSpot integration, Instantly connects to Salesforce, Apollo pushes to dozens of CRMs. These are point-and-click. Custom integrations use API calls through automation platforms (n8n, Make) or code (Python, JavaScript) to build connections that don't exist natively.
For GTM Engineers, understanding APIs is a career multiplier. The $45K coding premium in salary data connects directly to this skill. You don't need to be a software engineer, but you need to read API documentation, make HTTP requests, handle authentication (API keys, OAuth), and parse JSON responses.
Common API patterns in GTM: REST APIs (most common, use HTTP methods like GET and POST), GraphQL (used by some modern tools for flexible queries), and webhook-based APIs (push data when events happen). Rate limits are the practical constraint: most APIs restrict how many calls you can make per minute or hour. Working within rate limits while processing thousands of records is a core GTM engineering skill.