Hello Marta,
I understand that you are referring to the workflow of publishing geoprocessing tools as web tools/geoprocessing services. If that is the case, an ArcGIS Enterprise portal deployment is required to publish and host web tools. It is not possible to do so with a Developer Account in ArcGIS Online.
Hope this helps!
Best regards and stay safe,
Kanin
If this answer is helpful, please mark it as helpful. If this answer solved your question, please mark it as the answer to help others who have the same question.