REA is an open-source MCP server and CLI that lets AI coding agents like Claude Code, Codex and Cursor inspect apps without their source code. It works with native binaries through Hopper, Ghidra or IDA, and with JavaScript and Electron apps, .NET assemblies, Android apps and websites. The agent can then explain how a feature works, show the evidence behind each conclusion and build a similar version for your project. Analysis runs locally, and setup is a single npx command.