API Evangelist enhancements for Greenbrier Tank Car Gauge Table API

overlay: 1.0.0
info:
  title: API Evangelist enhancements for Greenbrier Tank Car Gauge Table API
  version: 1.0.0
  description: 'Records the enhancements API Evangelist applied on top of the derived contract for Greenbrier Tank
    Car Gauge Table API. The base document itself is left untouched. Provenance: Derived from the provider''s own
    shipped AngularJS client and confirmed by live probe; no Greenbrier-published spec exists.'
extends: openapi/greenbrier-cos-gauge-table-api-openapi.yml
actions:
- target: $.info
  description: Stamp third-party provenance on the contract.
  update:
    x-api-evangelist-profile: https://apis.io/provider/greenbrier-cos
    x-api-evangelist-provenance: Derived from the provider's own shipped AngularJS client and confirmed by live
      probe; no Greenbrier-published spec exists.
    x-first-party-spec: false
    x-verified-on: '2026-09-12'
- target: $
  description: Record the estate-level facts a consumer needs before calling.
  update:
    x-authentication: none - every catalogued operation answers an anonymous GET
    x-rate-limits: none published, none signalled at runtime
    x-support-channel: https://www.gbrx.com/contact-us/ (corporate contact form; no API support channel exists)
    x-status-page: null
    x-changelog: null
- target: $.paths.*.get
  description: Mark every catalogued operation as safe and repeatable - the public surface is read-only.
  update:
    x-safe: true
    x-idempotent: true
    x-consequence: read-only
- target: $.paths['/api/car/{mark}/{carNumber}/gauge-table'].get
  description: 'Flag the estate''s most dangerous error semantic: an unknown car is answered as HTTP 200 with a
    JSON null body, so a client that branches on the status code reads ''not held'' as success.'
  update:
    x-null-body-on-miss: true
    x-agent-caution: Do not branch on the status code. Parse the body and test for null before use.
- target: $.paths['/api/car/{mark}/{start}/-/{end}/valid-car-number-list'].get
  description: Record the observed unbounded response size so a client bounds the range itself.
  update:
    x-unpaginated: true
    x-observed-max-response: 982 KB / 20,049 records for GBRX 700000-724234, observed 2026-09-12