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.

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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

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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

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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."

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Supported backends

Backend	Status	Probe hardware
J-Link	Working (v0)	SEGGER J-Link (EDU, EDU Mini, PLUS, PRO, etc.)
OpenOCD	Planned	ST-Link, CMSIS-DAP, and many others
pyOCD	Planned	CMSIS-DAP, ST-Link, J-Link (via pyOCD)

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.

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Tools

Category	Tools
Probe	dbgprobe.probes.list, dbgprobe.connect, dbgprobe.erase, dbgprobe.disconnect, dbgprobe.reset, dbgprobe.halt, dbgprobe.go, dbgprobe.step, dbgprobe.status, dbgprobe.flash, dbgprobe.mem.read, dbgprobe.mem.write, dbgprobe.breakpoint.set, dbgprobe.breakpoint.clear, dbgprobe.breakpoint.list
Introspection	dbgprobe.connections.list
ELF	dbgprobe.elf.attach, dbgprobe.elf.info, dbgprobe.elf.lookup, dbgprobe.elf.symbols
SVD	dbgprobe.svd.attach, dbgprobe.svd.info, dbgprobe.svd.read, dbgprobe.svd.write, dbgprobe.svd.set_field, dbgprobe.svd.update_fields, dbgprobe.svd.list_peripherals, dbgprobe.svd.list_registers, dbgprobe.svd.list_fields, dbgprobe.svd.describe
RTT	dbgprobe.rtt.start, dbgprobe.rtt.stop, dbgprobe.rtt.read, dbgprobe.rtt.write, dbgprobe.rtt.status
Plugins	dbgprobe.plugin.list, dbgprobe.plugin.template, dbgprobe.plugin.load, dbgprobe.plugin.reload
Tracing	dbgprobe.trace.status, dbgprobe.trace.tail

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

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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

Variable	Default	Description
DBGPROBE_BACKEND	jlink	Debug probe backend. Future: openocd, pyocd.
DBGPROBE_MCP_LOG_LEVEL	WARNING	Python log level (DEBUG, INFO, WARNING, ERROR). Logs go to stderr.
DBGPROBE_MCP_TRACE	enabled	JSONL tracing of every tool call. Set to 0, false, or no to disable.
DBGPROBE_MCP_TRACE_PAYLOADS	disabled	Include memory data payloads in traced args (stripped by default).
DBGPROBE_MCP_TRACE_MAX_BYTES	16384	Max payload chars before truncation (only when TRACE_PAYLOADS is on).
DBGPROBE_MCP_TOOL_SEPARATOR	.	Character used to separate tool name segments. Set to _ for MCP clients that reject dots in tool names (e.g. Cursor).
DBGPROBE_MCP_PLUGINS	disabled	Plugin policy: all or comma-separated plugin names (e.g. nrf52,stm32).

J-Link backend

Variable	Default	Description
DBGPROBE_JLINK_PATH	auto-detect	Explicit path to JLinkExe (or JLink.exe on Windows).
DBGPROBE_JLINK_GDBSERVER_PATH	auto-detect	Explicit path to JLinkGDBServerCLExe.
DBGPROBE_JLINK_DEVICE	(none)	Default target device string (e.g. nRF52840_xxAA). Can be overridden per-session.
DBGPROBE_INTERFACE	SWD	Debug interface: SWD or JTAG.
DBGPROBE_SPEED_KHZ	4000	Interface clock speed in kHz.
DBGPROBE_GDB_TRACE	disabled	Log all GDB RSP packets to file. Set to 1, true, or yes to enable.
DBGPROBE_GDB_TRACE_FILE	/tmp/gdb_trace.log	Path for GDB RSP trace log (only when GDB_TRACE is on).

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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.

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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.

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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.

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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.

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Try without an agent

You can test the server interactively using the MCP Inspector:

npx @modelcontextprotocol/inspector python -m dbgprobe_mcp_server

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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)

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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.

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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.

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License

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