MCP JS Debugger

Establishes a new debugging session by connecting to a Chrome DevTools Protocol (CDP) endpoint. Use this to connect to Node.js (started with --inspect), Chrome, Edge, or other CDP-compatible runtimes. Returns a session_id that must be used in all subsequent debugging operations.

Closes an active debugging session and releases all resources. Any breakpoints set in the session will be removed.

Sets a breakpoint at a specific location in the code. The breakpoint will pause execution when the specified line is reached. You can set conditional breakpoints that only trigger when an expression evaluates to true.

Removes a previously set breakpoint. Use list_breakpoints to find breakpoint IDs.

Lists all breakpoints set in a debugging session, including their locations and conditions.

Resumes execution after being paused at a breakpoint or by pause_execution. Execution continues until the next breakpoint or the program ends.

Steps over the current statement to the next line in the same function. If the current line contains a function call, the entire function executes without stepping into it. The session must be paused.

Steps into a function call if the current line contains one, otherwise steps to the next statement. Use this to examine what happens inside a function. The session must be paused.

Steps out of the current function and pauses at the calling code. Use this to quickly exit a function you've stepped into. The session must be paused.

Pauses execution at the next possible opportunity. Use this when the program is running and you want to inspect its state.

Retrieves the current call stack when execution is paused. Shows the chain of function calls that led to the current location, including function names, file locations, and scope information. If source maps are available, original source locations are included.

Evaluates a JavaScript expression in the context of a specific call frame or global context. Use this to inspect variables, test expressions, or understand the program state. The expression is evaluated in the JavaScript runtime, so you can call methods, access properties, etc.

Retrieves all variables in a specific scope. Use this to see all local variables, closure variables, or global variables at a given point in execution.

Modifies the value of a variable in a specific call frame. Use this to test different scenarios or fix values during debugging.

Configures whether the debugger should pause when exceptions are thrown. Useful for catching errors as they occur.

Maps a generated code location back to the original source location using source maps. Essential for debugging bundled or transpiled code (TypeScript, Babel, webpack, esbuild, etc.).

Retrieves the source code for a script. If source maps are available, can return the original source instead of the generated/bundled code.

Lists all scripts loaded in the debugging session. Includes source map information where available, showing which original sources are mapped.