Circuit REST API Version 2

Create or register a Circuit app in the Circuit developer portal, then use that app's OAuth 2.0 flow to obtain an access token for the REST API. The public REST OpenAPI documents operations under a single oauth security scheme and lists OAuth scopes such as READ_CONVERSATIONS. The linked developer home at Circuit Developers is the vendor's developer portal, but the page could not be read anonymously during discovery, so exact registration clicks could not be confirmed.