Natural language processing can be used to create tools that help writing. Such tools can proofread the text and find spelling mistakes or stylistic problems. The style and spell checker could also verify that the text follows the set rules of a controlled language. NLP tools could be also used for information extraction to find the keywords of the text or perhaps even to automatically create a summary.
Although the APIs available on this site at the moment do not include any spell or style checkers, there are ready solutions available for these. Please use the contact form to ask for more information about these.