Debug Probe MCP Server

A stateful debug probe Model Context Protocol (MCP) server for developer tooling and AI agents. Works out of the box with Claude Code, VS Code with Copilot, and any MCP-compatible runtime. Communicates over stdio and drives on-chip debug probes (J-Link first, OpenOCD and pyOCD planned) to flash, debug, and inspect embedded targets.

Example: Let Claude Code list attached J-Link probes, connect to your nRF52840, flash a new firmware, read memory, and reset the target — all conversationally.

Demo

Video walkthrough — connecting to a J-Link probe, flashing firmware, loading ELF and SVD for symbol-aware debugging, RTT logging, and breakpoints.

Why this exists

If you've ever typed J-Link Commander commands by hand, copy-pasted memory addresses between a datasheet and a terminal, re-flashed the same firmware 20 times during a debug session, and juggled multiple tool windows — this is for you.

You have a microcontroller on a debug probe. You want an AI agent to interact with it — connect, flash firmware, read/write memory, reset, halt, resume. This server makes that possible.

It gives any MCP-compatible agent a full set of debug probe tools. The agent calls these tools, gets structured JSON back, and reasons about what to do next — without you manually driving JLinkExe for every operation.

What agents can do with it:

• Flash and iterate — build firmware, flash it, reset, check behavior — all in one conversation
• Inspect memory — read peripheral registers, check RAM contents, verify flash writes
• Debug interactively — halt, step, set breakpoints, inspect state, resume
• Automate test flows — flash → reset → read output → validate
• Multi-probe setups — connect to multiple probes simultaneously, each with its own session

Who is this for?

• Embedded engineers — faster iteration: flash, debug, inspect memory conversationally
• Hobbyists and makers — interact with microcontrollers without learning JLinkExe command syntax
• QA and test engineers — automated flash-and-test sequences across multiple boards
• Researchers — systematic exploration of embedded systems, register inspection

Quickstart (Claude Code)

pip install dbgprobe-mcp-server

# Register the MCP server with Claude Code
claude mcp add dbgprobe -- dbgprobe_mcp

# Or with explicit J-Link path
claude mcp add dbgprobe \
  -e DBGPROBE_JLINK_PATH=/Applications/SEGGER/JLink/JLinkExe \
  -- dbgprobe_mcp

Then in Claude Code, try:

"List attached debug probes, connect to the J-Link, and read 16 bytes from address 0x20000000."

Supported backends

The server is backend-agnostic — tool names (dbgprobe.*) stay the same regardless of which probe you use.

J-Link requirements

Install the SEGGER J-Link Software Pack. The server auto-detects JLinkExe on PATH or in common install locations:

• macOS: /Applications/SEGGER/JLink/
• Linux: /opt/SEGGER/JLink/, /usr/bin/
• Windows: C:\Program Files\SEGGER\JLink\

Or set DBGPROBE_JLINK_PATH to point to the executable directly.

This project is not affiliated with or sponsored by SEGGER. J-Link is used because it's widely available and well-supported.

Tools

See docs/tools.md for full schemas and examples.

Install (development)

# Editable install from repo root
pip install -e ".[test]"

# Or with uv
uv pip install -e ".[test]"

MCP is a protocol — this server works with any MCP-compatible client. Below are setup instructions for the most common ones.

Add to Claude Code

# Standard setup
claude mcp add dbgprobe -- dbgprobe_mcp

# With default target device
claude mcp add dbgprobe \
  -e DBGPROBE_JLINK_DEVICE=nRF52840_xxAA \
  -- dbgprobe_mcp

# Debug logging
claude mcp add dbgprobe -e DBGPROBE_MCP_LOG_LEVEL=DEBUG -- dbgprobe_mcp

Add to VS Code / Copilot

Add to your project's .vscode/mcp.json (or create it):

{
  "servers": {
    "dbgprobe": {
      "type": "stdio",
      "command": "dbgprobe_mcp",
      "args": [],
      "env": {
        "DBGPROBE_JLINK_DEVICE": "nRF52840_xxAA"
      }
    }
  }
}

Adjust env to match your target — set DBGPROBE_JLINK_DEVICE to your chip, or remove it to specify the device at connect time.

Add to Cursor

Add to your project's .cursor/mcp.json (or create it). Cursor does not support dots in tool names, so DBGPROBE_MCP_TOOL_SEPARATOR must be set to _:

{
  "mcpServers": {
    "dbgprobe": {
      "command": "dbgprobe_mcp",
      "args": [],
      "env": {
        "DBGPROBE_JLINK_DEVICE": "nRF52840_xxAA",
        "DBGPROBE_MCP_TOOL_SEPARATOR": "_"
      }
    }
  }
}

Environment variables

Server

J-Link backend

ELF Support

Attach an ELF file to a session to enable symbol-aware debugging:

• Symbol lookup — resolve function names to addresses and vice versa
• Breakpoints by name — breakpoint.set(symbol="main") instead of raw addresses
• Auto-enriched responses — status, step, and halt include symbol + symbol_offset when an ELF is attached
• Flash integration — flashing an .elf auto-attaches it; flashing .hex/.bin auto-reloads a previously attached ELF; sibling .elf files are suggested via hints

> "Attach the ELF, set a breakpoint on main, run, and show me where it halted."

The agent calls elf.attach, breakpoint.set(symbol="main"), go, then status — and gets back "halted at main+0" instead of a raw hex address.

SVD Support

Attach an SVD (System View Description) file to a session to enable register-level peripheral access:

• Named register reads — svd.read("GPIO.OUT") returns the raw value and all decoded fields with enum names
• Field-level reads — svd.read("GPIO.PIN_CNF[3].PULL") returns the field value and enum name ("PullUp")
• Safe field writes — svd.set_field("GPIO.PIN_CNF[3].PULL", "PullUp") does read-modify-write
• Batch field updates — svd.update_fields("GPIO.PIN_CNF[3]", {"DIR": "Output", "PULL": "PullUp"}) — one read, one write
• Raw register writes — svd.write("GPIO.OUT", 0x01) — full register, no RMW
• Discovery — list peripherals, registers, fields; describe with enums
• Auto-decode on mem.read — when an SVD is attached and mem.read hits a known register address, the response includes decoded fields

> "Attach the SVD, read GPIO.PIN_CNF[3], and set PULL to PullUp."

The agent calls svd.attach, svd.read("GPIO.PIN_CNF[3]"), then svd.set_field("GPIO.PIN_CNF[3].PULL", "PullUp") — and gets back decoded field values instead of raw hex.

RTT (Real-Time Transfer)

Start, stop, read, and write to SEGGER RTT channels. The agent can stream target log output and send data to the device — useful for debugging firmware that prints over RTT instead of UART.

> "Start RTT and show me the output."

For repetitive flows — read device ID, run a self-test sequence, validate calibration — you can package them as plugins: Python modules that expose custom tools the agent can call directly. Enable with DBGPROBE_MCP_PLUGINS=all. See the nrf52_info example.

Tracing

Every tool call is traced to .dbgprobe_mcp/traces/trace.jsonl and an in-memory ring buffer (last 2000 events). Tracing is on by default — set DBGPROBE_MCP_TRACE=0 to disable.

Use dbgprobe.trace.status and dbgprobe.trace.tail to inspect the trace without reading the file directly.

Try without an agent

You can test the server interactively using the MCP Inspector:

npx @modelcontextprotocol/inspector python -m dbgprobe_mcp_server

Roadmap / TODO

• OpenOCD backend — support ST-Link, CMSIS-DAP, and other probes via OpenOCD subprocess
• pyOCD backend — native Python probe access via pyOCD library
• Multi-core support — target specific cores on multi-core SoCs
• Cortex-A/R support — ARM-mode breakpoints (kind=4); currently Thumb-only (Cortex-M)

Known limitations

• Single-client only. The server handles one MCP session at a time (stdio transport).
• RTT channel 0 only. RTT support is limited to channel 0 (terminal). Multi-channel RTT is a future enhancement.
• Flash clears breakpoints. Flashing new firmware invalidates breakpoints (the code at those addresses may have changed). The session stays alive but breakpoints are cleared.
• Cortex-M only. Breakpoints use Thumb-mode (kind=2). Cortex-A/R targets (ARM-mode, kind=4) are not yet supported.
• Instruction-level step only. dbgprobe.step single-steps one CPU instruction. Source-level stepping (step into/over/out) is not supported.

Safety

This server connects an AI agent to real debug hardware. That's the point — and it means the stakes are higher than pure-software tools.

Plugins execute arbitrary code. When plugins are enabled, the agent can create and run Python code on your machine with full server privileges. Review agent-generated plugins before loading them.

Writes affect real hardware. A bad memory write or flash operation can brick a device, wipe calibration data, or trigger unintended behavior. Consider what the agent can reach.

Use tool approval deliberately. When your MCP client prompts you to approve a tool call, consider whether you want to allow it once or always.

This software is provided as-is under the MIT License. You are responsible for what the agent does with your hardware.

License

This project is licensed under the MIT License — see LICENSE for details.