Get device info

Instructions

Implementation Reference

• src/joulescope_mcp/server.py:50-60 (registration)

  The MCP tool registration for 'device_info' using @mcp.tool decorator. Defines the tool's title, description, annotations (read_only), structured output, and parameters (device_path, include_metadata). Delegates to service.device_info().

  @mcp.tool(
      title="Get device info",
      description="Return retained device topics and optional metadata for one JouleScope.",
      annotations=read_only,
      structured_output=True,
  )
  def device_info(device_path: str | None = None, include_metadata: bool = False) -> dict[str, Any]:
      try:
          return service.device_info(device_path=device_path, include_metadata=include_metadata)
      except JoulescopeMcpError as exc:
          raise _tool_error(exc) from exc

• src/joulescope_mcp/service.py:167-197 (handler)

  The actual handler logic for device_info in Js220Service. Opens a driver session, selects a device, subscribes to retained publications (pub_retain) and optionally metadata (metadata_rsp_retain), strips the device prefix from topic keys, and returns device_path, values dict, and optional metadata dict.

  def device_info(self, device_path: str | None = None, include_metadata: bool = False) -> dict[str, Any]:
      values: dict[str, Any] = {}
      metadata: dict[str, Any] = {}
  
      def on_pub(topic: str, value: Any) -> None:
          values[topic] = _jsonable(value)
  
      def on_metadata(topic: str, value: Any) -> None:
          metadata[topic[:-1] if topic.endswith("$") else topic] = _jsonable(value)
  
      with self._driver_session() as driver:
          device = self._select_device(driver, device_path=device_path, require_js220=False)
          driver.open(device, mode="restore")
          try:
              driver.subscribe(device, "pub_retain", on_pub)
              driver.unsubscribe(device, on_pub)
              if include_metadata:
                  driver.subscribe(device, "metadata_rsp_retain", on_metadata)
                  driver.unsubscribe(device, on_metadata)
          finally:
              driver.close(device)
  
      def strip_prefix(items: dict[str, Any]) -> dict[str, Any]:
          prefix = device + "/"
          return {k[len(prefix) :] if k.startswith(prefix) else k: v for k, v in sorted(items.items())}
  
      return {
          "device_path": device,
          "values": strip_prefix(values),
          "metadata": strip_prefix(metadata) if include_metadata else None,
      }

• src/joulescope_mcp/service.py:167-168 (schema)

  Function signature showing input parameters: device_path (str | None, default None) and include_metadata (bool, default False). Return type is dict[str, Any] with keys 'device_path', 'values', and 'metadata'.

  def device_info(self, device_path: str | None = None, include_metadata: bool = False) -> dict[str, Any]:
      values: dict[str, Any] = {}

• src/joulescope_mcp/service.py:189-191 (helper)

  Helper function strip_prefix used within device_info to remove the device path prefix from topic keys for cleaner output.

  def strip_prefix(items: dict[str, Any]) -> dict[str, Any]:
      prefix = device + "/"
      return {k[len(prefix) :] if k.startswith(prefix) else k: v for k, v in sorted(items.items())}