fixup

* add description
* nix the confusing "expected"/"actual" nomenclature in favor of "configured"/"sliced" and
* use the nomenclature correctly in the error message

macros.cfg

@@ -235,12 +235,13 @@ gcode:
   G0 X{safe_x} Y{y} F{speed}
 
 [gcode_macro ASSERT_NOZZLE_DIAMETER]
+description: Raises an error unless the configured nozzle diameter is the same as the diameter passed in.
 gcode:
-  {% set expected_diameter = params.NOZZLE_DIAMETER|float %}
-  {% set actual_diameter = printer.configfile.config.extruder.nozzle_diameter|float %}
-  {% if expected_diameter != actual_diameter %}
+  {% set configured_diameter = printer.configfile.config.extruder.nozzle_diameter|float %}
+  {% set sliced_diameter = params.NOZZLE_DIAMETER|float %}
+  {% if configured_diameter != sliced_diameter  %}
     M117 Aborting print due to nozzle-diameter mismatch between printer config and slicer.
-    { action_raise_error("Nozzle-diameter mismatch between printer config (%s mm) and slicer (%s mm)." % (expected_diameter, actual_diameter)) }
+    { action_raise_error("Nozzle-diameter mismatch between printer config (%s mm) and slicer (%s mm)." % (configured_diameter, sliced_diameter)) }
   {% endif %}
 
 #####