Which IBM Watson service is pre-trained and does not allow for any customization?

The Tone Analyzer is the service that is pre-trained and does not allow for any customization. It is designed to analyze text for emotional tone—such as joy, anger, sadness, and more—based on a predefined set of models and algorithms. This service operates using its existing training and does not offer users the ability to modify the underlying models or customize them with additional training data.

In contrast, the other services mentioned allow for varying degrees of customization. For instance, Natural Language Understanding can be adapted by providing it with custom classifiers or models to better suit specific needs. Speech to Text allows for customization in terms of adding vocabulary or tuning the system to better understand specific voices or accents. Similarly, Discovery offers customization options to enhance its data processing capabilities tailored to particular datasets or domains.