API (Application Programming Interface)

A defined way for software components to talk to each other — usually over the network — using requests, responses, and documented rules.

An API is a contract. One system exposes endpoints or operations; another system calls them with agreed parameters and receives structured data or status codes. Web APIs today are often REST or GraphQL over HTTPS, but the idea applies equally to libraries and operating systems: predictable inputs and outputs that hide complexity behind a stable boundary.

Good API design matters for security and reliability. Authentication (who is calling), authorization (what they may do), rate limits, versioning, and clear error messages reduce outages and integration pain. Documentation — whether OpenAPI specs or developer portals — is part of the product, not an afterthought.

For AI and automation, APIs are how models and agents connect to your data, tools, and workflows. Treating APIs as first-class interfaces — tested, monitored, and evolved carefully — keeps human-facing apps and machine clients equally dependable.