Author(s): “The AI Engineer”
Originally published on Towards AI.
created by GEMINI
For thirty years, the API was the contract. One system exposed a fixed set of endpoints, another system called them in a known order, and both sides agreed on the shape of the data flowing between them. That contract worked because both sides were, fundamentally, static. Your billing service didn’t wake up one morning and decide to query the inventory service in a different sequence. It called what it was told to call, when it was told to call it.
Agents broke that assumption. An autonomous agent doesn’t consume an API the way a script does — it reasons about which capability it needs, discovers whether something can provide it, and adapts its call pattern based on intermediate results. The traditional API was never built to be discovered, negotiated with, or reasoned about. It was built to be read in documentation and hard-coded.
