The service gives lists of articles that exist in one language, but not another. However, it doesn't handle passing in a domain as a parameter, rather it takes a source language and a destination language. Apart from the conceptual problem, in practice when calling the MW Action API, it needs to supply a domain in the request. As it does not, the MW API returns a 404.
I propose to fix this problem by declaring the target language to be the domain. In practical terms, that means that the end points would become:
- /{domain}/v1/translation/articles/{source}
- /{domain}/v1/translation/articles/{source}/{seed}
Here, {domain} denotes the target language's domain. This is in line with T107914: Migrate content translation to the REST API where we will be using the target wiki's domain as the main one.