systeminformer-mcp

An MCP server that exposes System Informer's capabilities as tools: processes, threads, modules, handles, memory, services, network endpoints, drivers, windows and file signatures — plus process launching and control.

54 tools, verified end-to-end on Windows 11 (build 26200).

How it works

Modern System Informer builds have no headless command mode — the old -ctype / -cobject / -caction switches were removed, and the remaining command line switches only configure the GUI. Scraping a GUI would be both fragile and lossy.

So this server does what System Informer itself does: it calls the same native NT APIs directly (NtQuerySystemInformation, NtQueryInformationProcess, NtDuplicateObject, the SCM APIs, iphlpapi, WinVerifyTrust, …) through ctypes. Results come back as structured JSON rather than table rows.

The installed System Informer application is still used for two things:

• GUI hand-off — launch_systeminformer_gui, launch_peview for the live graphs and interactive views that do not translate to tool output.
• dbghelp.dll — the copy shipped with System Informer writes process dumps.

Neither is required. If System Informer is not installed, every inspection and control tool still works; only those two hand-off tools become unavailable.

Install

pip install mcp

Then register the server with your MCP client. For Claude Code — note the PYTHONPATH, which is what lets python -m si_mcp find the package from any working directory:

claude mcp add systeminformer --scope user -e PYTHONIOENCODING=utf-8 -e "PYTHONPATH=C:\path\to\systeminformer-mcp" -- python -m si_mcp

Or add it to your client's config file directly:

{
  "mcpServers": {
    "systeminformer": {
      "command": "python",
      "args": ["-m", "si_mcp"],
      "env": {
        "PYTHONIOENCODING": "utf-8",
        "PYTHONPATH": "C:\\path\\to\\systeminformer-mcp"
      }
    }
  }
}

Alternatively pip install -e . from the project root, which puts a systeminformer-mcp console script on PATH and makes PYTHONPATH unnecessary.

Set SYSTEMINFORMER_PATH if System Informer is installed somewhere other than C:\Program Files\SystemInformer.

Privileges

Windows, not this server, decides what is visible. Run the server elevated for full coverage — call server_status at any time to see exactly what is and is not available:

Running as	What you get
Standard user	Your own processes in full; other users' processes are limited
Elevated	Nearly everything: all processes, kernel addresses, service control
Elevated + KSystemInformer driver	Protected processes (PPL, antimalware) too

Unelevated, Windows withholds kernel addresses (driver base addresses read back as 0x0) and thread start addresses for processes you do not own. The server works around the latter by re-querying through a thread handle where it can.

Tools

System — system_overview, system_cpu_usage, system_memory, system_uptime

Processes — list_processes, process_tree, process_details, process_token, process_modules, process_threads, thread_details

Process control — launch_process, launch_process_elevated, terminate_process, terminate_process_tree, suspend_process, resume_process, set_process_priority, set_process_affinity, set_process_critical, empty_working_set, create_process_dump

Threads — suspend_thread, resume_thread, terminate_thread, set_thread_priority, set_thread_affinity

Memory — process_memory_regions, process_memory_summary, read_process_memory, write_process_memory, protect_process_memory, search_process_memory, process_memory_strings

Handles — list_handles, handle_type_summary, find_handles_by_name, close_handle

Services — list_services, service_details, control_service, set_service_start_type, create_service, delete_service

Network — network_connections, port_owner

Drivers & windows — list_drivers, list_windows, window_action

Files — file_details, verify_file_signature

System Informer — server_status, launch_systeminformer_gui, launch_peview

Examples

"What's using port 3000?"                  -> port_owner
"Which process has this DLL locked?"       -> find_handles_by_name
"Why is my machine at 100% CPU?"           -> list_processes sort_by=cpu
"Start notepad minimized, then suspend it" -> launch_process, suspend_process
"Is this binary signed?"                   -> verify_file_signature

Safety

Tools that cannot be undone, or that can destabilise a running process, require an explicit confirm=true:

• write_process_memory — can corrupt or crash the target
• close_handle — the owning process is not told its handle vanished
• terminate_process_tree — kills every descendant
• delete_service — service registration cannot be restored by this server
• set_process_critical — terminating a critical process bugchecks Windows

launch_process_elevated routes through the standard Windows UAC consent prompt. This server never accepts, stores or transmits credentials; to run a process as a different user, use the System Informer GUI's Run As dialog.

Notes on correctness

A few details that are easy to get wrong and are handled here:

• Object names can hang. Naming a handle means duplicating it and calling NtQueryObject, which blocks forever on a synchronous named pipe whose peer never answers. Like System Informer, this runs on a worker thread with a timeout; a wedged worker is retired rather than reused, and the handle is deliberately leaked instead of being closed out from under the blocked call.
• Process names are not NUL-terminated. SYSTEM_PROCESS_INFORMATION carries an explicit Length; decoding by scanning for a terminator reads past the string into adjacent data and yields unpaired UTF-16 surrogates. All tool output is additionally sanitized so no malformed name from another process can fail a response.
• Token structures embed pointers into their own buffer. TOKEN_USER and friends must be read from a live allocation, not a copied bytes.
• Fixed-size info classes reject over-sized buffers. SystemBasicInformation and the per-processor tables want exactly the size the running kernel expects, which differs across Windows versions, so the size is queried first.
• PID reuse breaks process trees. A "parent" created after its child is treated as recycled, and the child is reported at the root.

Tests

python tests/test_e2e.py

Starts the server over real MCP stdio transport, calls a tool from every group, and round-trips a live process: launch → inspect → suspend → resume → dump → terminate. It also asserts that each guarded tool refuses to act without confirm=true. 44 checks.