Agents are just APIs. Nothing fundamental has changed. A copilot calling your API is still a client making a request to an endpoint that returns a response, and every bit of the discipline still applies — authentication, rate limits, schema validation, governance, documentation.
What has changed is the consumer, and the consumer is less forgiving. A human developer will read around a vague field name, guess from an example, and email support when stuck. A model will not. It will pick the wrong operation, hallucinate a parameter, and fail in a way nobody debugs.
So agent-ready means: a precise, accurate OpenAPI. JSON Schema with real types, constraints, and descriptions on every field — the description is the thing the model actually reasons over. Capabilities described as tasks rather than as CRUD over your tables. Documented errors, including what the agent should do about each one. Documented rate limits, returned in headers so the agent can back off. Workflows described in Arazzo where an outcome takes several calls. And machine-readable discovery so all of that is findable without a human.
Notice that every one of those is something that was already good practice. The agentic turn did not invent a new discipline; it raised the cost of skipping the old one.
