Node.js Debugger MCP
An MCP server for the Node.js debugger: breakpoints, stepping, variable inspection and expression evaluation at a pause
- 350 ★ on the repository
- Last commit
- MIT
Broad access
Why this level
- The server launches a Node.js script on your machine with debugger access to the process
- The evaluate_expression tool runs arbitrary JavaScript in the paused process
- Variables and console output may contain secrets, which then reach the agent and the model
Install
- Works in
Manual install
{
"devtools-debugger-mcp": {
"command": "devtools-debugger-mcp"
}
}For a global install: npm install -g devtools-debugger-mcp. Or use command node with args pointing to dist/index.js after npm install devtools-debugger-mcp.
Access and checks
How we reviewBroad accessThe tool can change data, run commands or handle secrets.
- The server launches a Node.js script on your machine with debugger access to the process
- The evaluate_expression tool runs arbitrary JavaScript in the paused process
- Variables and console output may contain secrets, which then reach the agent and the model
This is third-party code. Review the repository files before installing.
What it does
For Node.js programs, the server gives an agent the same debugging abilities that Chrome DevTools and VS Code offer. It launches your script with the `--inspect-brk=0` flag, waits for the inspector WebSocket and attaches over the Chrome DevTools Protocol. The agent gets back the first pause with an identifier and the top stack frame. The agent then sets breakpoints by file path or by URL regex, as well as conditional breakpoints and logpoints. It can turn on pause-on-exceptions and drive execution: step over, into or out, run to a location and restart a frame. At a pause it reads locals with closures and object properties, the call stack and console output since the last step, and evaluates expressions in the chosen frame. The server understands source maps, so TypeScript and other transpiled code can be debugged too. Responses come as `text`, `json` or both. There are over twenty tools, from `start_node_debug` to `stop_debug_session`.
Who it is for. For Node.js developers who want the agent to trace the cause of a failure in a running process using real variable values.
Good fit when
- A script crashes on an exception and the agent must stop at that point and show variable values
- You need a conditional breakpoint that fires only for one user or request
- You want a logpoint without editing the code, to watch values as it runs
- The code is TypeScript with source maps and debugging should follow the original lines
- You need to test a hypothesis about an expression's value in a specific stack frame
Not a fit when
- You need to debug a browser page or Python: the server launches only Node.js scripts
- You need to attach to a process that is already running, for example in production: the server debugs only scripts it launches itself
- Logs and the error stack are enough and you do not need to pause execution
- You want debugging inside the editor with your launch.json: VS Code extensions cover that
Example request
Launch /abs/path/app.js under the debugger, set a breakpoint on line 42, run to it and show the local variables and user.nameMCP
- Transport
- stdio
- Authentication
- not required
Limitations
The server debugs only Node.js programs that it launches itself through `start_node_debug`: the process starts paused on the first line, and the agent drives it from there. Debugging browser pages and other languages is out of scope.
There are no ready instructions for specific clients; setup comes down to a generic MCP config block. The last commit in the repository dates from October 2025, so check compatibility with your Node.js version on a small script first.
How to disable. Remove the devtools-debugger-mcp block from your MCP client settings and restart the client. Uninstall the package with `npm uninstall devtools-debugger-mcp`. An active debugging session is closed by the `stop_debug_session` tool.
FAQ
How do I connect a Node.js debugger to an agent?
Install the package with `npm install devtools-debugger-mcp` and add a block to your MCP settings with the `node` command and the path to `dist/index.js`, or with the global `devtools-debugger-mcp` command. After a client restart the agent gets the debugging tools.
How do I start a debugging session?
Call `start_node_debug` with the absolute path to the script. The server launches Node with `--inspect-brk=0`, attaches to the inspector and pauses on the first line. Then set breakpoints and call `resume_execution`.
Can I debug TypeScript?
Yes. The server supports source maps, so breakpoints and steps follow the original lines of transpiled code.
What is a logpoint?
A conditional breakpoint that writes a message to the console and returns false, so execution does not stop. `add_logpoint` creates it, and `read_console` reads the messages.
How do I control the response size?
The `set_output_format` tool sets the default response format: `text`, `json` or both. Every tool also accepts the same `format` parameter. Stepping and resume have flags that add scopes, stack and console to the reply.
Discussion
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Comparison with similar tools
Entries that share the main search query, and how they differ.
| Entry | Official | Authentication | Repository stars | Main difference |
|---|---|---|---|---|
| Node.js Debugger MCP (this entry) | no | not required | 350 | |
| DebugMCP | yes | not required | 577 | Microsoft's official server: a VS Code extension and CLI with breakpoints for many languages |
| Claude Debugs For You | no | not required | 514 | a VS Code extension with an MCP server that debugs through your launch.json |
| Chrome DevTools MCP | yes | not required | 54,432 | the Chrome DevTools team's official server for a live browser, network and console |
README in short
The description explains why an assistant benefits from debugger access and lists the features. Installation, a config block, a step-by-step example in six calls and a reference for each tool with its parameters follow.