stinger-python-utils 0.1.8

Common utilities for Stinger Python services.

stinger-python-utils

Shared utilities for Stinger Python services, providing convenient message creation for MQTT communication.

Installation

uv add stinger-python-utils

MessageCreator

MessageCreator is a utility class for creating MQTT messages with standardized properties and payloads.

Basic Usage

from pydantic import BaseModel
from stinger_python_utils.message_creator import MessageCreator

class MyPayload(BaseModel):
    name: str
    value: int

payload = MyPayload(name="test", value=42)
message = MessageCreator.signal_message("my/topic", payload)

Methods

Method	Purpose	Return Code
signal_message(topic, payload)	Send a signal with one-time delivery	QoS 1, no retain
status_message(topic, payload, expiry_seconds)	Send status that expires	QoS 1, retained, with expiry
error_response_message(topic, return_code, correlation_id, debug_info)	Error response to a request	QoS 1, user properties: ReturnCode
response_message(topic, payload, return_code, correlation_id)	Successful response to a request	QoS 1, user properties: ReturnCode
property_state_message(topic, payload, state_version)	Publish property state	QoS 1, retained, JSON content type
property_update_request_message(topic, payload, version, response_topic, correlation_id)	Request property update	QoS 1, user property: PropertyVersion
property_response_message(topic, payload, version, return_code, correlation_id, debug_info)	Respond to property update	QoS 1, user properties: ReturnCode, PropertyVersion
request_message(topic, payload, response_topic, correlation_id)	Send a request (auto-generates UUID if no correlation_id)	QoS 1, auto correlation ID

Example: Request/Response Pattern

from pydantic import BaseModel
from stinger_python_utils.message_creator import MessageCreator

class Request(BaseModel):
    action: str

request = Request(action="start")
msg = MessageCreator.request_message(
    "devices/cmd",
    request,
    response_topic="devices/response"
)
# Returns a Message with auto-generated correlation ID

Example: Error Response

msg = MessageCreator.error_response_message(
    "devices/response",
    return_code=500,
    correlation_id="req-123",
    debug_info="Device not found"
)
# User properties include: ReturnCode=500, DebugInfo=Device not found

---

MCP Server

stinger-python-utils includes an optional Model Context Protocol (MCP) server that exposes stinger-ipc services to AI coding assistants such as GitHub Copilot in VS Code.

The server discovers live stinger-ipc service instances over MQTT and dynamically registers them as MCP resources (properties and signal mailboxes) and tools (methods and writable property setters). Functionality is provided by plugins — third-party packages that register against the stinger_python_utils.mcp_plugins stevedore entry-point namespace.

Installation

Install with the mcp extra to pull in the MCP SDK, stevedore, and uvicorn:

pip install 'stinger-python-utils[mcp]'
# or with uv:
uv add 'stinger-python-utils[mcp]'

MQTT Connection Configuration

The server connects to an MQTT broker using environment variables:

Variable	Default	Description
MQTT_HOST	localhost	Broker hostname or IP
MQTT_PORT	1883	Broker port
MQTT_TRANSPORT	tcp	tcp, websocket, or unix
MQTT_CLIENT_ID	(random)	MQTT client identifier

Running the Server

stdio transport (recommended for VS Code / Copilot):

stinger-mcp-server --transport stdio

SSE transport (for browser-based or remote clients):

stinger-mcp-server --transport sse --host 0.0.0.0 --port 8000

Adding to VS Code (GitHub Copilot)

Add the server to your VS Code user or workspace MCP configuration.

Option 1 — User settings (~/.vscode/mcp.json or via Settings → MCP):

{
  "servers": {
    "stinger": {
      "type": "stdio",
      "command": "stinger-mcp-server",
      "args": ["--transport", "stdio"],
      "env": {
        "MQTT_HOST": "localhost",
        "MQTT_PORT": "1883"
      }
    }
  }
}

Option 2 — Workspace settings (.vscode/mcp.json in your repo, checked into source control so the whole team shares the same configuration):

{
  "servers": {
    "stinger": {
      "type": "stdio",
      "command": "stinger-mcp-server",
      "args": ["--transport", "stdio"],
      "env": {
        "MQTT_HOST": "localhost",
        "MQTT_PORT": "1883"
      }
    }
  }
}

Once saved, open the Copilot Chat panel, switch to Agent mode, and the stinger service tools and resources will be available.

Tip: If stinger-mcp-server is installed inside a virtual environment rather than globally, use the full path to the executable, e.g. "/path/to/.venv/bin/stinger-mcp-server".

Option 3 — SSE transport (connect to a server already running elsewhere, e.g. on a remote device or in a container):

First start the server with the SSE transport:

MQTT_HOST=192.168.1.100 stinger-mcp-server --transport sse --host 0.0.0.0 --port 8000

Then point VS Code at it in .vscode/mcp.json:

{
  "servers": {
    "stinger": {
      "type": "sse",
      "url": "http://localhost:8000/sse"
    }
  }
}

Replace localhost with the hostname or IP of the machine running the server.

Writing a Plugin

Plugins provide the actual service-type knowledge to the MCP server. Create a class that extends StingerMCPPlugin and register it as a stevedore entry-point:

my_service/mcp_plugin.py:

from stinger_python_utils.mcp import (
    StingerMCPPlugin,
    SignalDefinition,
    PropertyDefinition,
    MethodDefinition,
)
from .client import MyServiceClient
from .discoverer import MyServiceDiscoverer

class MyServicePlugin(StingerMCPPlugin):

    def get_plugin_name(self) -> str:
        return "my_service"  # used as URI scheme: my_service://instance/...

    def get_discovery_class(self) -> type:
        return MyServiceDiscoverer

    def get_client_class(self) -> type:
        return MyServiceClient

    def get_signals(self) -> list[SignalDefinition]:
        return [
            SignalDefinition(name="status_changed", description="Emitted when device status changes"),
        ]

    def get_properties(self) -> list[PropertyDefinition]:
        return [
            PropertyDefinition(
                name="brightness",
                schema={
                    "type": "object",
                    "properties": {"value": {"type": "integer", "minimum": 0, "maximum": 100}},
                    "required": ["value"],
                },
                readonly=False,
                description="Brightness level (0–100)",
            ),
        ]

    def get_methods(self) -> list[MethodDefinition]:
        return [
            MethodDefinition(
                name="restart",
                arguments_schema={"type": "object", "properties": {}},
                description="Restart the device",
            ),
        ]

pyproject.toml of the plugin package:

[project.entry-points."stinger_python_utils.mcp_plugins"]
my_service = "my_service.mcp_plugin:MyServicePlugin"

Install the plugin package into the same environment as stinger-python-utils[mcp] and the server will discover it automatically on next start.

MCP Resource and Tool Naming

For each discovered service instance the server exposes:

MCP primitive	Name / URI pattern	Description
Resource	{plugin}://{instance_id}/property/{name}	Current property value (JSON)
Resource	{plugin}://{instance_id}/signal/{name}	Mailbox of the last 10 signals (JSON array with timestamps)
Tool	{plugin}_{instance_id}_{method_name}	Calls a method on the instance
Tool	{plugin}_{instance_id}_set_{property_name}	Sets a writable property

As instances come and go the tool and resource lists update automatically.