OpenAPI

In short

A machine-readable description of an HTTP API, usually openapi.json or openapi.yaml. Example: On seven sites that shipped one, agents fetched openapi.json in 112 of 541 runs, or 21 percent. Related terms: Optional section, Markdown twin. Optional section: An H2 named Optional in llms.txt that holds secondary links. v2 keeps it as a convention and drops its special meaning for tools.