The Jina Reader API is a tool designed to convert URLs into Markdown, making them more suitable for grounding large language models (LLMs). It simplifies the process by extracting the core content from web pages, excluding unnecessary elements like scripts. This service also supports PDF extraction and provides automatic image captioning, enhancing the readability of the content. Furthermore, the Reader API is scalable, offering high concurrency and reliability, and it's available for free with flexible rate limits.