WE Multitool DUT MCP

multitool-mcp is a dependency-free Model Context Protocol server for inspecting and debugging a device under test (DUT) through a Wise Electronics WE Multitool.

It runs over standard input/output and bridges the Multitool's JSON-over-WebSocket API. It exposes bounded MCP tools for GPIO, I2C, SPI, UART, PWM, GPIO ownership, SWD debugging, and SWO trace. SWD/SWO tools manage a host OpenOCD process connected to the Multitool CMSIS-DAP TCP probe.

Requirements

• Python 3.11 or later
• A WE Multitool reachable over WebSocket

Install

Install from PyPI once published:

python -m pip install multitool-mcp

For development from a clone:

python -m pip install -e .

Configure an MCP client

Run the installed command:

[mcp_servers.we_multitool_dut]
command = "multitool-mcp"
env_vars = ["WE_MULTITOOL_URL", "WE_MULTITOOL_TIMEOUT_SECONDS"]
startup_timeout_sec = 10
tool_timeout_sec = 150
default_tools_approval_mode = "prompt"

By default, the server connects to ws://we-multitool.local/ws. Set these environment variables before starting the MCP client to change that:

WE_MULTITOOL_URL=ws://10.0.0.1/ws
WE_MULTITOOL_TIMEOUT_SECONDS=8

On PowerShell:

$env:WE_MULTITOOL_URL = "ws://10.0.0.1/ws"
$env:WE_MULTITOOL_TIMEOUT_SECONDS = "8"

Safety and firmware behavior

Read pins_get before configuring pins, and verify wiring, voltage, bus role, and DUT limits before driving signals.

gpio_configure accepts input, output, and open-drain directions. Open-drain mode requires firmware with open-drain GPIO setup support and an appropriate external pull-up.

• Commands are serialized because firmware responses do not carry request IDs.
• UART data received while another command awaits a response is buffered.
• The gpio_set firmware command has no acknowledgement; gpio_write reports it as dispatched but unverified.
• The firmware tracks one active WebSocket response socket. Do not use the browser UI and MCP bridge concurrently.

SWD and SWO

Version 0.2.0 adds these tools:

Install an OpenOCD build with the CMSIS-DAP TCP backend. The Espressif build used here supports it; some stock 0.12.0 builds do not. Python still requires no runtime packages. Provide trusted local OpenOCD configuration files that select CMSIS-DAP TCP port 4441, read the host from WE_MULTITOOL_HOST, and configure the target. The server sets this environment variable from its WebSocket URL. Target flash algorithms and SWO pin routing belong in these files.

OpenOCD GDB/Tcl/trace ports bind to localhost (defaults 3333/6666/3443). Only one OpenOCD client can connect to the probe: stop a VSCode debug session before starting an MCP session. MCP client shutdown stops its owned process and normally resumes a halted DUT. Stopping a session keeps probe pins reserved; swd_disable releases them to inputs. Use direct wiring only with 3.3 V compatible targets and a shared ground.

Hardware verification

MCP tools were tested on the connected Nucleo L452: probe enable/disable/status, OpenOCD startup/cleanup, halt/resume/reset, single-step in debug_init, and two matching 64-byte Flash reads at requested 4 MHz. SWO at 100 kbaud with an 80 MHz trace clock returned 184 raw bytes / 92 ITM port-0 bytes, including the startup banner, with zero reported overflow packets or decoder errors. This MCP smoke test did not reflash the target.

Single-step waits for the target to halt again. Stepping a sleeping RTOS idle instruction can time out; the tool reports an error instead of reporting successful completion while the target is still running.

SWO reads return raw base64/hex, decoded itm_ports with text and payload bytes, overflow counts, and decoder errors. Decoding persists across reads, including split packets and UTF-8 sequences. Hardware event and timestamp packets are not interpreted as text. A quiet read can return zero bytes. No lossless throughput is promised; overflow counts describe ITM overflow packets, not every possible capture loss.

Memory writes and flashing are marked destructive. Flashing verifies an existing ELF and resets the target; it does not automatically remove protection. Set the MCP client tool timeout to at least 150 seconds for flash operations. Requested SWD speed is not a measurement of the physical clock. Prior direct OpenOCD tests on this L452 passed repeated reads at requested 4 MHz; retest your wiring before using a higher speed.

After installing the updated server, restart the MCP client to discover the new tools. To use this checkout on Windows, set its MCP command to D:/_projects/wise-electronics/multitool-mcp/.venv/Scripts/multitool-mcp.exe after installing with .venv/Scripts/python.exe -m pip install -e ..

Development

python -m pip install -e ".[test]"
python -m pytest

The runtime has no third-party dependencies. The optional test extra installs pytest.

License

Licensed under the GNU General Public License, version 3 or later (GPL-3.0-or-later). See LICENSE.