With the last DeepL API (Pro), the Rephrase "function" with input in EN (English) and asked for DE (German) with Tone=Confident returns a string in English

[RegisBarbier]

Describe the bug
With the last DeepL API (Pro), the Rephrase "function" with input in EN (English) and asked for DE (German) with Tone=Confident returns a string in English

To Reproduce
Steps to reproduce the behavior:
URL:
{{baseUrl}}/v2/write/rephrase
Request:
{
    "text": [
        "Adapt our test cases for having them more modular and lighter."
     ],
    "source_lang": "EN",
    "target_lang": "DE",
    "writing_style": "default",
    "tone": "confident"
}
2. Check the returned JSON data
3. See error:
Response: STATUS = 200
{
    "improvements": [
        {
            "text": "Adapt your test cases to make them more modular and lighter.",
            "detected_source_language": "de",
            "target_language": "de"
        }
    ]
}

Expected behavior
I expect there an improvement (rephrase) written in German, which is the case with the same input in ENglish and Output asked in German and every other Writing_style or Tone.
Only with an input in English like "Adapt our test cases for having them more modular and lighter.", with source_lang = EN, target_lang=DE and Writing_style=default and tone=confident is producting this issue. with other allowed target languages I did not see any issue at this time.

Screenshots or sample code

Additional context
N/A

Thank you very much in advance for solving this issue.
Best regards

[JanEbbing]

The text you send to v2/write/rephrase should be in the same language you want, we currently dont have an endpoint that can translate and rephrase at the same time (you'd need to make a call to v2/translate and one to /v2/write/rephrase sequentially). See docs, e.g. source_lang as a parameter does not exist on this endpoint at all (unfortunately we don't give explicit error messages in these cases but just silently ignore these... Something we can hopefully fix in a v3 version)

[JanEbbing]

For the request you made, I think using v2/translate to go from EN->DE and then v2/write/rephrase sounds like the best solution to me.

[RegisBarbier]

Sorry, my mistake: the parameter source_lang was used in a translate request, not there.
This case without source_lang is also providing the same result with tone=confident.

If I enter another sentence (also in English), I get the right one in German with the parameters "target_lang=DE" and "tone=confident". The "Rephrase/ImproveText" function is then running correctly. :-)

I think that I was may be using a special sentence causing this behavior.

Thank you very much for your answer.
You can then close this ticket.

[JanEbbing]

Yeah, the write models (on v2/write/rephrase) do learn some level of translation capability during our training, but it will be poor quality compared to the dedicated v2/translate. But as you noticed it might not be stable once you also incorporate styles or tones. Closing for now, feel free to reopen if you run into issues