OpenAPI Specification

Overview

OpenAPI Specification is a standard, machine-readable description format for HTTP APIs, including paths, operations, parameters, schemas, responses, and security schemes. It is used to make API contracts portable across documentation, code generation, testing, and governance tools. It differs from API documentation as a whole, which also includes tutorials, workflows, operational guidance, and support policy.

A typical implementation works as follows: Teams author or generate an OpenAPI document, validate it in delivery pipelines, publish it to developer tools, and compare changes before release. Changes to OpenAPI Specification should be checked against older clients, stored payloads, enum growth, default behavior, and retry assumptions.

Common risks include an incomplete or stale document can generate unsafe clients and hide behavior not represented by schemas. Important failure modes include an incomplete or stale document. These failures can generate unsafe clients, hide behavior not represented by schemas, or create false confidence in compatibility.

Core controls require teams to treat the document as versioned source, lint and test it, review breaking changes, protect examples, and keep runtime behavior aligned. A successful transport result from OpenAPI Specification should not be interpreted beyond the exact API state documented by the provider.

Operational evidence should include OpenAPI version, document revision, service release, validation result, diff result, and owner. OpenAPI Specification should be documented alongside API Definition, API Schema, and API Documentation. Data handled by OpenAPI Specification should use documented types, units, timestamp rules, nullable fields, and enum behavior to prevent silent interpretation errors.

The OpenAPI Specification owner should publish stable error semantics and guidance on whether correction, retry, status lookup, or escalation is appropriate.