How an agent finds a paid endpoint: .well-known/x402.json, llms.txt and an MCP server card

The llms.txt proposal received a major revision in August 2026 to help agents locate the file describing a specific page. This Markdown file provides agents with a curated entry point, including a name and short summary. Additionally, discovery artifacts like .well-known/x402.json and MCP server cards assist agents in finding paid endpoints. These files prevent agents from guessing routes and body shapes on human-centric landing pages, facilitating processes like paying for HTTP requests via x402.