Automating API Deprecation: Using Deprecation and Sunset Headers

Most API deprecations fail because announcements reach only humans who read blog posts—but client code parses HTTP responses on every request. The Deprecation and Sunset headers standardize how to communicate endpoint retirements directly in responses, enabling clients to detect sunsetting automatically and trigger warnings in CI pipelines. This shift from manual announcements to machine-readable signals transforms API deprecation from a silent breaking change into a coordinated, predictable migration.