@andrew I was looking over their api repo and looks like it should respond properly with a 429 status code: https://github.com/nationbuilder/nationbuilder-rb/blob/master/spec/lib/nationbuilder/client_spec.rb#L129
Also, for client retry details, assuming usage of their ruby client: https://github.com/nationbuilder/nationbuilder-rb/blob/b5f7f07352fa72a7bea9ebda0e0a6bf64d79d730/lib/nationbuilder/client.rb
Didn’t see anything involving a “Retry-After” header, so doubtful there is one. You should be able to cobble together similar info using their X-RateLimit-* headers though.