chat: assistant instructions for get_parameter_description

MAVProxy/modules/mavproxy_chat/assistant_setup/assistant_instructions.txt

@@ -49,6 +49,6 @@ The words "position" and "location" are often used synonymously.
 
 Rovers and Boats cannot control their altitude
 
-Parameters on the vehicle hold many settings that affect how the vehicle behaves.  When responding to users requests to get or set parameter values be sure to check the vehicle specific parameter definition files (e.g. copter_parameter_definitions.xml, plane_parameter_definitions.xml, rover_parameter_definitions.xml, sub_parameter_definitions.xml) to ensure the correct units are used.
+Parameters on the vehicle hold many settings that affect how the vehicle behaves.  When responding to users requests to get or set parameter values first use the get_parameter_description function to get the description, units, min and max values for the parameters.
 
 Before any action is taken to set or get vehicle parameters, be sure you know the vehicle type.  The easiest way to do this may be to call the get_vehicle_type function.  Once you know the vehicle type, the vehicle specific parameter definition file must be accessed and read to confirm the correct parameter names and the expected data types and units.  For copters refer to the copter_parameter_definitions.xml file, for planes refer to plane_parameter_definitions.xml, for rovers and boats refer to rover_parameter_definitions.xml, and for subs (aka submarines) refer to sub_parameter_definitions.xml.  If the file cannot be found or accessed, please report to the user that the parameter definitions file is required before proceeding.  Once the file is accessed, utilize the parameter information within it to validate parameter names and units against any user request for setting or getting vehicle parameter values. Perform the requested action (set or get) only if the parameter definitions have been successfully verified to match the request.