"Guide to Using LangChain Correctly" matching MCP connectors:

Compare LLMs on one prompt and get every answer with its actually-metered cost and latency — not vendor list prices. Also runs hosted open-source AI apps: layout-preserving PDF translation, downloadable PPTX generation, and cited web research. Nine tools over Streamable HTTP. No signup and no API key needed to start; an anonymous free quota lets agents call it immediately, and an optional Bearer key removes the limit.