File format

How a contract file is checked and parsed: its keys, extension, documents, anchors and comments.

Every key at every level is checked against the grammar of Write contracts and Schemas. A key the grammar does not know, such as options, an uppercase GET or a top-level version, is a violation. The report lists every violation in every file, and nothing is stored.
The extension must be .yaml or .yml. The CLI refuses a file passed with anything else before contacting the broker: unsupported contract file extension: "petstore_api.txt". Inside a folder, files with any other extension are skipped.
One YAML document per file. A second document after --- is rejected with malformed contract file: petstore_api.yaml: multiple documents are not supported.
YAML anchors and aliases are rejected with malformed contract file: petstore_api.yaml: anchors and aliases are not supported. To reuse a shape, name it under schemas and point to it with ref.
YAML comments are allowed. They are ignored when the file is parsed.

How the file is published, and what the broker answers, is in publish.