Update Write API docs for new capabilities

api-reference/improve-text.mdx

@@ -60,20 +60,21 @@ curl -X POST 'https://api.deepl.com/v2/write/rephrase' \
 
 <ParamField body="text" type="array[string]" required>
   Text to be improved. Only UTF-8-encoded plain text is supported. Improvements are returned in the same order as they are requested. Each of the parameter values may contain multiple sentences.
-
-  All texts **must** be in the same language.
 </ParamField>
 <ParamField body="target_lang" type="string">
-  The language of the improved text. A list of supported languages have not yet been added to the `/languages` endpoint. At the time of the beta, the following languages are supported:
+  The language of the improved text. A list of supported languages have not yet been added to the `/languages` endpoint. Currently, the following languages are supported:
 
   * `de` (German)
   * `en-GB` (British English)
   * `en-US` (American English)
   * `es` (Spanish)
   * `fr` (French)
   * `it` (Italian)
+  * `ja` (Japanese)
+  * `ko` (Korean)
   * `pt-BR` (Brazilian Portuguese)
   * `pt-PT` (Portuguese)
+  * `ZH`/`zh-Hans` (simplified Chinese)
 
   The language of the source texts sent in the `text` parameter must match the target language (translating and improving text simultaneously is not yet supported).
 
@@ -97,9 +98,15 @@ curl -X POST 'https://api.deepl.com/v2/write/rephrase' \
   </Expandable>
   Currently supported for the following target languages:
 
-  * `de`
-  * `en-GB`
-  * `en-US`
+  * `de` (German)
+  * `en-GB` (British English)
+  * `en-US` (American English)
+  * `es` (Spanish)
+  * `fr` (French)
+  * `it` (Italian)
+  * `pt-BR` (Brazilian Portuguese)
+  * `pt-PT` (Portuguese)
+
 
   Styles prefixed with `prefer_` will fall back to the `default` style when used with a language that does not support styles (this is recommended for cases where no `target_lang` is set), the non-prefixed writing styles (except `default`) will return a HTTP 400 error in that case.
 
@@ -124,9 +131,14 @@ curl -X POST 'https://api.deepl.com/v2/write/rephrase' \
 
   Currently supported for the following target languages:
 
-  * `de`
-  * `en-GB`
-  * `en-US`
+  * `de` (German)
+  * `en-GB` (British English)
+  * `en-US` (American English)
+  * `es` (Spanish)
+  * `fr` (French)
+  * `it` (Italian)
+  * `pt-BR` (Brazilian Portuguese)
+  * `pt-PT` (Portuguese)
 
   Tones prefixed with `prefer_` will fall back to the `default` tone when used with a language that does not support tones (this is recommended for cases where no `target_lang` is set), the non-prefixed tones (except `default`) will return a HTTP 400 error in that case.
 

docs/resources/roadmap-and-release-notes.mdx

@@ -11,6 +11,12 @@ rss: true
 </Update>
 
 <Update label="March 2026">
+## March 27 - Write API Improvements
+- Improved overall quality of the models used in [DeepL API for Write](/api-reference/improve-text/)
+- Expanded Write `target_lang` support to Japanese (`JA`), Korean (`KO`) and simplified Chinese (`ZH` or `zh-Hans`)
+- Expanded Write support for `writing_style` and `tone` to Spanish (`ES`), Italian (`IT`), French (`FR`), Portuguese (`pt-PT`) and Brazilian Portuguese (`pt-BR`)
+- Allow sending Write texts in multiple source languages in the same request when no `target_lang` is set
+
 ## March 26 - Expanded Style Rules API
 - Added 5 new endpoints for style rule list operations: `POST /v3/style_rules`, `GET /v3/style_rules/{style_id}`, `PATCH /v3/style_rules/{style_id}`, `DELETE /v3/style_rules/{style_id}`, and `PUT /v3/style_rules/{style_id}/configured_rules`.
 - Added 4 new endpoints for managing custom instructions within style rule lists: `POST /v3/style_rules/{style_id}/custom_instructions`, `GET /v3/style_rules/{style_id}/custom_instructions/{instruction_id}`, `PUT /v3/style_rules/{style_id}/custom_instructions/{instruction_id}`, and `DELETE /v3/style_rules/{style_id}/custom_instructions/{instruction_id}`.