Reverse API Engineer

Reverse API Engineer (rae) is an MIT-licensed command-line tool by kalil0321 that turns websites into API clients. You give it a site and a goal, a browser is driven by you or by an AI agent, traffic is captured to a HAR file, and your configured model writes a working client. The latest release listed on GitHub is v0.14.0, which added PowerShell support and Windows compatibility.

What It Is

Reverse API Engineer is a reverse-engineering assistant for undocumented HTTP APIs. Instead of opening DevTools, copying cURL commands and assembling a client by hand, you browse a site and the tool maps the backend calls the site actually makes. Output is plain source files written into your project, with a generated README and a runnable example, in Python, JavaScript, TypeScript, Go, Java, C#, PHP, Ruby, C, or PowerShell.

How the Capture Workflow Works

The CLI has four modes you cycle with Shift+Tab: manual (you drive a local Playwright browser), agent (an AI agent browses autonomously), engineer (re-run generation on a previous capture), and collector (an agent gathers structured JSON/CSV data using web search and fetch). Agent mode can use Playwright MCP, Chrome DevTools MCP (drives your real Chrome with existing sessions), or the Vercel agent-browser CLI.

Generated Output

The docs describe generated clients with type hints, authentication handling (cookies, bearers, CSRF tokens), pagination helpers, error types, and inline documentation. Runs are saved under ~/.reverse-api/runs/ with message logs, and token usage and cost are tracked per run.

Model and Agent Backends

The tool uses Claude by default and can route through OpenCode (including Ollama models via OpenCode), GitHub Copilot, or Cursor SDK backends when optional dependencies and credentials are configured. Scriptable subcommands (agent, engineer, run, list, show) support JSON output and NDJSON streaming so other agents or CI jobs can drive captures.

Tradeoffs to Know

The README advises reviewing generated code before executing it, and notes that sites with aggressive bot detection may block capture or need manual interaction. Intel macOS and 32-bit Windows are not supported installation platforms.