The tool 'pdf gpt' functions primarily as a PDF summarization tool using the GPT AI model. It allows users to upload PDF files and generates a detailed summary of the entire document. The uniqueness of this system comes from its ability to process whole PDFs, rather than smaller sections, which enables it to create summaries that are significantly richer in detail. The tool breaks down the PDF into a comprehensive summary, a table of contents, and individual summaries for each distinct section of the document. It's noteworthy that to fully utilize this tool, users must have JavaScript enabled.