Free tool
Free llms.txt generator
Paste your sitemap URL and get an llms.txt file that lists your pages in the format proposed at llmstxt.org. It runs in your browser and needs no account.
What an llms.txt file does
llms.txt is an unofficial convention proposed at llmstxt.org, not a standard the AI engines have adopted, and publishing one has no demonstrated effect on how often AI answers cite a site. This tool only formats your own pages in that convention.
Whether AI assistants can read your site at all is decided by your robots.txt, your sitemap and your pages. Start there: how to check whether AI assistants can crawl your site.