This repository serves as a comprehensive documentation project that provides deep-dive insights into the architecture, internals, and usage of various AI-powered CLI tools. It documents five specific tools: Claude Agent SDK, Gemini CLI, Codex CLI, OpenCode, and Pi Coding Agent, offering detailed explanations of their internal workings, features, and integration patterns. The content is derived from direct source code analysis and aims to fill the gaps in official documentation. The repository is structured with dedicated directories for each tool, following a standardized numbering convention for topics (e.g., 01-overview, 02-technical-stack). It also includes specialized extraction sections for the Claude Agent SDK, breaking down its subsystems into individually documented 'complete' files. This approach demonstrates a reproducible pattern for knowledge extraction from complex software systems. While the repository excels in organizing and presenting technical information, it relies on external source code for its content and does not include the analysis scripts or raw data used to generate the documentation. This makes reproducing the exact analysis challenging, though the documented versions of each tool are specified. The documentation faces a high risk of becoming outdated due to the rapid evolution of the underlying AI CLI tools.