Documentation is often the first source, which can help user to solve problems or provide conditions of use of some product. That is why it should be clear and understandable. But what does “understandable” mean? And how to detect whether some text is unclear? And this thesis can answer on those questions.The main idea of current work is to measure clarity of the text information using natural language processing capabilities. There are three global steps to achieve this goal: to define criteria of bad clarity of text information, to evaluate different natural language toolkits and find suitable for us, and to implement a prototype system that, given a text, measures text clarity.Current thesis project is planned to be included to VizzAnalyzer (quality analysis tool, which processes information on structure level) and its main task is to perform a clarity analysis of text information extracted by VizzAnalyzer from different XML-files.