return0
@getreturn0
Debug your remote Node.js and Next.js applications directly from your AI IDE like Cursor.
Overview
What is return0?
return0 is an MCP server for debugging production Node.js applications in real-time. It integrates with Cursor IDE to monitor variables, observe execution flow, and understand runtime behavior in live environments, especially for Next.js apps deployed on platforms like Vercel.
How to use return0?
Install by configuring the MCP server in Cursor IDE. Use the one‑click install button or manual setup by adding a server named return0 with command npx, args -y @return-0/mcp-server, and environment variable RETURN0_API_KEY set to your API key. Provide an API key (or "demo" for testing) to authenticate.
Key features of return0
- Provides a
variable_extractortool for extracting runtime variable values. - Reads source files from the local filesystem.
- Uses TypeScript AST analysis to correct variable line numbers.
- Connects to live production applications to retrieve runtime data.
- Returns real‑time variable values, types, and timestamps.
Use cases of return0
- Debug production Node.js applications without redeploying.
- Monitor live variable values in Next.js apps on Vercel.
- Troubleshoot runtime behavior directly from Cursor IDE.
- Extract and inspect variables at specific line numbers in production code.
FAQ from return0
How do I get an API key for return0?
Visit the return0 documentation to obtain your API key. You can also use "demo" for testing purposes.
What tool does return0 provide?
It provides a variable_extractor tool that extracts the runtime value, type, and timestamp of variables from production code based on file paths and variable names with line numbers.
How do I configure return0 in Cursor IDE?
You can either use the one‑click installation button or manually add a server with name return0, command npx, args -y @return-0/mcp-server, and the environment variable RETURN0_API_KEY. See the manual configuration steps in the README.
What are the runtime requirements for return0?
Node.js and npm are required because the server runs via npx and is installed automatically when Cursor starts.
Where does my production variable data live?
The MCP server reads source files from your local filesystem and connects to your running production application to retrieve live variable values. Data is not stored persistently by the server.
