Optic

Optic is a command-line tool that helps keep OpenAPI specifications accurate. It catches breaking changes between versions of an API, applies lint rules, and verifies that the implementation matches the specification.

OpenAPI documents can be generated from test traffic, and automatic schema testing compares real requests and responses with the specification and proposes patches. Breaking changes and lint rules are checked with the same tool, for example on pull requests in CI. References and specifications split across several files are supported.

Optic is open source under the MIT licence. Its GitHub repository was archived in January 2026 and the tool is no longer maintained.