Swagger CLI is a deprecated command‑line tool that validates Swagger 2.0 and OpenAPI 3.0 specification files (JSON or YAML) and can bundle multiple related API definitions—using `$ref` references or full dereferencing—into a single output file. Its primary users are developers who need to lint, verify, and combine OpenAPI specifications, though the project points them toward the more actively maintained Redocly CLI for newer use cases.