some hints

code/modules/atmospherics/machinery/airalarm.dm

@@ -233,6 +233,12 @@
 
 	power_change()
 	set_frequency(frequency)
+	register_context()
+
+/obj/machinery/airalarm/add_context(atom/source, list/context, obj/item/held_item, mob/living/user)
+	. = ..()
+	LAZYSET(context[SCREENTIP_CONTEXT_ALT_LMB], INTENT_ANY, locked ? "Unlock" : "Lock")
+	return CONTEXTUAL_SCREENTIP_SET
 
 /obj/machinery/airalarm/Destroy()
 	SSradio.remove_object(src, frequency)

code/modules/atmospherics/machinery/atmosmachinery.dm

@@ -41,6 +41,10 @@
 	var/on = FALSE
 	var/interacts_with_air = FALSE
 
+/obj/machinery/atmospherics/Initialize(mapload)
+	. = ..()
+	register_context()
+
 /obj/machinery/atmospherics/examine(mob/user)
 	. = ..()
 	if(is_type_in_list(src, GLOB.ventcrawl_machinery) && isliving(user))
@@ -48,6 +52,17 @@
 		if(SEND_SIGNAL(L, COMSIG_CHECK_VENTCRAWL))
 			. += "<span class='notice'>Alt-click to crawl through it.</span>"
 
+/obj/machinery/atmospherics/add_context(atom/source, list/context, obj/item/held_item, mob/living/user)
+	. = ..()
+
+	if(can_unwrench && held_item?.tool_behaviour == TOOL_WRENCH)
+		LAZYSET(context[SCREENTIP_CONTEXT_LMB], INTENT_ANY, "Unfasten")
+		. = CONTEXTUAL_SCREENTIP_SET
+
+	if(is_type_in_list(src, GLOB.ventcrawl_machinery) && isliving(user) && SEND_SIGNAL(user, COMSIG_CHECK_VENTCRAWL))
+		LAZYSET(context[SCREENTIP_CONTEXT_ALT_LMB], INTENT_ANY, "Crawl into")
+		. = CONTEXTUAL_SCREENTIP_SET
+
 /obj/machinery/atmospherics/New(loc, process = TRUE, setdir)
 	if(!isnull(setdir))
 		setDir(setdir)

code/modules/clothing/under/_under.dm

@@ -99,12 +99,13 @@
 		has_sensor = BROKEN_SENSORS
 		sensordamage = sensormaxintegrity
 
-/obj/item/clothing/under/New()
+/obj/item/clothing/under/Initialize(mapload)
 	if(sensor_flags & SENSOR_RANDOM)
 		//make the sensor mode favor higher levels, except coords.
 		sensor_mode = pick(SENSOR_OFF, SENSOR_LIVING, SENSOR_LIVING, SENSOR_VITALS, SENSOR_VITALS, SENSOR_VITALS, SENSOR_COORDS, SENSOR_COORDS)
 	sensor_mode_intended = sensor_mode
-	..()
+	register_context()
+	return ..()
 
 /obj/item/clothing/under/equipped(mob/user, slot)
 	..()
@@ -360,5 +361,20 @@
 
 	return TRUE
 
+/obj/item/clothing/under/add_context(atom/source, list/context, obj/item/held_item, mob/living/user)
+	. = ..()
+	if (!(item_flags & IN_INVENTORY))
+		return
+
+	if(!isliving(user) || !user.canUseTopic(src, BE_CLOSE, ismonkey(user)))
+		return
+
+	LAZYSET(context[SCREENTIP_CONTEXT_CTRL_LMB], INTENT_ANY, "Set to highest sensor")
+	if(attached_accessory)
+		LAZYSET(context[SCREENTIP_CONTEXT_ALT_LMB], INTENT_ANY, "Remove [attached_accessory]")
+	else
+		LAZYSET(context[SCREENTIP_CONTEXT_ALT_LMB], INTENT_ANY, "Adjust [src]")
+	return CONTEXTUAL_SCREENTIP_SET
+
 /obj/item/clothing/under/rank
 	dying_key = DYE_REGISTRY_UNDER

code/modules/modular_computers/computers/item/tablet.dm

@@ -36,6 +36,17 @@
 			inserted_item = new inserted_item(src)
 		else
 			inserted_item =	new /obj/item/pen(src)
+	register_context()
+
+/obj/item/modular_computer/tablet/add_context(atom/source, list/context, obj/item/held_item, mob/living/user)
+	. = ..()
+	if(can_have_pen)
+		if(inserted_item)
+			LAZYSET(context[SCREENTIP_CONTEXT_CTRL_LMB], INTENT_ANY, "Remove [inserted_item]")
+			. = CONTEXTUAL_SCREENTIP_SET
+		else if(is_type_in_list(held_item, contained_item))
+			LAZYSET(context[SCREENTIP_CONTEXT_LMB], INTENT_ANY, "Insert [held_item]")
+			. = CONTEXTUAL_SCREENTIP_SET
 
 /obj/item/modular_computer/tablet/proc/insert_pen(obj/item/pen)
 	if(!usr.transferItemToLoc(pen, src))

code/modules/power/apc.dm

@@ -290,6 +290,13 @@
 		set_machine_stat(stat | MAINT)
 		update_appearance()
 		addtimer(CALLBACK(src, .proc/update), 5)
+	register_context()
+
+/obj/machinery/power/apc/add_context(atom/source, list/context, obj/item/held_item, mob/living/user)
+	. = ..()
+	if(operating)
+		LAZYSET(context[SCREENTIP_CONTEXT_ALT_LMB], INTENT_ANY, locked ? "Unlock" : "Lock")
+		return CONTEXTUAL_SCREENTIP_SET
 
 /obj/machinery/power/apc/Destroy()
 	GLOB.apcs_list -= src

code/modules/reagents/reagent_containers/hypospray.dm

@@ -15,6 +15,16 @@
 	var/ignore_flags = 0
 	var/infinite = FALSE
 
+/obj/item/reagent_containers/hypospray/Initialize(mapload, vol)
+	. = ..()
+	register_item_context()
+
+/obj/item/reagent_containers/add_item_context(obj/item/source, list/context, atom/target, mob/living/user)
+	. = ..()
+	if(iscarbon(target))
+		LAZYSET(context[SCREENTIP_CONTEXT_LMB], INTENT_ANY, "Inject")
+		return CONTEXTUAL_SCREENTIP_SET
+
 /obj/item/reagent_containers/hypospray/attack_paw(mob/user)
 	return attack_hand(user)
 
@@ -378,6 +388,23 @@
 	if(start_vial)
 		vial = new start_vial
 	update_icon()
+	register_context()
+	register_item_context()
+
+/obj/item/hypospray/mkii/add_context(atom/source, list/context, obj/item/held_item, mob/living/user)
+	. = ..()
+	// Did you know that clicking something while you're holding it is the same as attack_self()?
+	if(vial && (held_item == src))
+		LAZYSET(context[SCREENTIP_CONTEXT_LMB], INTENT_ANY, "Remove [vial]")
+	LAZYSET(context[SCREENTIP_CONTEXT_CTRL_LMB], INTENT_ANY, "Set to [mode ? "spray" : "inject"]")
+	LAZYSET(context[SCREENTIP_CONTEXT_ALT_LMB], INTENT_ANY, "Set transfer amount")
+	return CONTEXTUAL_SCREENTIP_SET
+
+/obj/item/hypospray/mkii/add_item_context(obj/item/source, list/context, atom/target, mob/living/user)
+	. = ..()
+	if(iscarbon(target))
+		LAZYSET(context[SCREENTIP_CONTEXT_LMB], INTENT_ANY, mode ? "Inject" : "Spray")
+		return CONTEXTUAL_SCREENTIP_SET
 
 /obj/item/hypospray/mkii/ComponentInitialize()
 	. = ..()

code/modules/surgery/tools.dm

@@ -349,6 +349,16 @@
 	w_class = WEIGHT_CLASS_TINY
 	attack_verb = list("slapped")
 
+/obj/item/surgical_drapes/Initialize(mapload)
+	. = ..()
+	register_item_context()
+
+/obj/item/surgical_drapes/add_item_context(obj/item/source, list/context, atom/target, mob/living/user)
+	. = ..()
+	if(iscarbon(target))
+		LAZYSET(context[SCREENTIP_CONTEXT_LMB], INTENT_ANY, "Prepare Surgery")
+		return CONTEXTUAL_SCREENTIP_SET
+
 /obj/item/surgical_drapes/attack(mob/living/M, mob/user)
 	if(!attempt_initiate_surgery(src, M, user))
 		..()