AI tools including Perplexity and Open AI's GPT-4 often provide one-sided answers to contentious questions, and don't back up their arguments with reliable sources How well-supported are the claims made by AI tools? Generative AI tools, and the deep research agents and search engines powered by them, frequently make unsupported and biased claims that aren't backed up by the sources they cite. That's according to an analysis which found that about one-third of answers provided by the AI tools aren't backed up by reliable sources. For OpenAI's GPT 4.5, the figure was even higher, at 47 per cent. Alongside this, they put five deep research agents through their paces: GPT-5's Deep Research feature, Bing Chat's Think Deeper option and deep research tools offered by You.com, Google Gemini and Perplexity.