diff --git a/components/infobox/commons/infobox.lua b/components/infobox/commons/infobox.lua
index 7b22fb4e424..cc2ed123525 100644
--- a/components/infobox/commons/infobox.lua
+++ b/components/infobox/commons/infobox.lua
@@ -9,9 +9,12 @@
 local Array = require('Module:Array')
 local Class = require('Module:Class')
 local Logic = require('Module:Logic')
+local Lua = require('Module:Lua')
 local Variables = require('Module:Variables')
 local WarningBox = require('Module:WarningBox')
 
+local Widget = Lua.import('Module:Widget')
+
 ---@class Infobox
 ---@field frame Frame?
 ---@field root Html?
@@ -79,9 +82,7 @@ end
 ---@return Html
 function Infobox:build(widgets)
 	for _, widget in ipairs(widgets) do
-		if widget == nil or widget['is_a'] == nil then
-			error('Infobox:build can only accept Widgets')
-		end
+		assert(Class.instanceOf(widget, Widget), 'Infobox:build can only accept Widgets')
 
 		self.content:node(widget:tryMake(self.injector))
 	end
diff --git a/components/prize_pool/commons/prize_pool_base.lua b/components/prize_pool/commons/prize_pool_base.lua
index 5156ade16d4..eddfccdd239 100644
--- a/components/prize_pool/commons/prize_pool_base.lua
+++ b/components/prize_pool/commons/prize_pool_base.lua
@@ -919,7 +919,7 @@ end
 ---@param widgetInjector WidgetInjector An instance of a class that implements the WidgetInjector interface
 ---@return self
 function BasePrizePool:setWidgetInjector(widgetInjector)
-	assert(widgetInjector:is_a(WidgetInjector), 'setWidgetInjector: Not a Widget Injector')
+	assert(Class.instanceOf(widgetInjector, WidgetInjector), 'setWidgetInjector: Not a Widget Injector')
 	self._widgetInjector = widgetInjector
 	return self
 end
@@ -928,7 +928,7 @@ end
 ---@param lpdbInjector LpdbInjector An instance of a class that implements the LpdbInjector interface
 ---@return self
 function BasePrizePool:setLpdbInjector(lpdbInjector)
-	assert(lpdbInjector:is_a(LpdbInjector), 'setLpdbInjector: Not an LPDB Injector')
+	assert(Class.instanceOf(lpdbInjector, LpdbInjector), 'setLpdbInjector: Not an LPDB Injector')
 	self._lpdbInjector = lpdbInjector
 	return self
 end
diff --git a/components/squad/commons/squad_row.lua b/components/squad/commons/squad_row.lua
index 30f29f29a2d..0c51ad54c3b 100644
--- a/components/squad/commons/squad_row.lua
+++ b/components/squad/commons/squad_row.lua
@@ -22,7 +22,7 @@ local RoleIcons = {
 	sub = Icon.makeIcon{iconName = 'substitute', hover = 'Substitute'},
 }
 
----@class SquadRow
+---@class SquadRow: BaseClass
 ---@operator call(ModelRow): SquadRow
 ---@field children Widget[]
 ---@field model ModelRow
diff --git a/components/widget/widget.lua b/components/widget/widget.lua
index 28bc9cf88d6..6ccd37b692d 100644
--- a/components/widget/widget.lua
+++ b/components/widget/widget.lua
@@ -54,7 +54,7 @@ function Widget:tryChildren(injector)
 		children = self:makeChildren(injector) or {}
 	end
 	return Array.map(children, function(child)
-		if type(child) == 'table' and type(child['is_a']) == 'function' and child:is_a(Widget) then
+		if Class.instanceOf(child, Widget) then
 			---@cast child Widget
 			return Logic.tryOrElseLog(
 				function() return child:tryMake(injector) end,
diff --git a/standard/class.lua b/standard/class.lua
index bb7fc56d20d..0065995560e 100644
--- a/standard/class.lua
+++ b/standard/class.lua
@@ -6,10 +6,6 @@
 -- Please see https://github.com/Liquipedia/Lua-Modules to contribute
 --
 
----
--- @author Vogan for Liquipedia
---
-
 local Arguments = require('Module:Arguments')
 
 local Class = {}
@@ -18,7 +14,8 @@ Class.PRIVATE_FUNCTION_SPECIFIER = '_'
 
 ---@class BaseClass
 ---@operator call:self
----@field is_a fun(self, BaseClass):boolean
+---@field is_a fun(self, class: BaseClass):boolean #deprecated
+---@field init fun(self, ...)
 
 function Class.new(base, init)
 	local instance = {}
@@ -59,16 +56,9 @@ function Class.new(base, init)
 		return Class.export(instance, options)
 	end
 
-	instance.is_a = function(self, class)
-		local m = getmetatable(self)
-		while m do
-			if m == class then
-				return true
-			end
-			m = m._base
-		end
-		return false
-	end
+	---@deprecated
+	instance.is_a = Class.instanceOf
+
 	setmetatable(instance, metatable)
 	return instance
 end
@@ -159,4 +149,18 @@ function Class._frameToArgs(frame, options)
 	return (Table.isNotEmpty(namedArgs) and namedArgs or nil), indexedArgs
 end
 
+---@param instance any
+---@param class BaseClass
+---@return boolean
+function Class.instanceOf(instance, class)
+	local metatable = getmetatable(instance)
+	while metatable do
+		if metatable == class then
+			return true
+		end
+		metatable = metatable._base
+	end
+	return false
+end
+
 return Class
diff --git a/standard/condition.lua b/standard/condition.lua
index 3ff8f44371b..0ee410c05b4 100644
--- a/standard/condition.lua
+++ b/standard/condition.lua
@@ -34,7 +34,7 @@ local ConditionTree = Class.new(_ConditionNode,
 function ConditionTree:add(node)
 	if not node then
 		return self
-	elseif node.is_a ~= nil and node:is_a(_ConditionNode) then
+	elseif Class.instanceOf(node, _ConditionNode) then
 		table.insert(self._nodes, node)
 	else
 		-- List of nodes
@@ -50,7 +50,7 @@ function ConditionTree:toString()
 	assert(self.booleanOperator ~= nil)
 	return table.concat(Array.map(self._nodes,
 		function(node)
-			if node:is_a(ConditionTree) then
+			if Class.instanceOf(node, ConditionTree) then
 				return String.interpolate('(${node})', {node = node:toString()})
 			end
 
@@ -66,7 +66,6 @@ end
 ---@field name ColumnName
 ---@field comparator lpdbComparator
 ---@field value string|number
----@field is_a function
 local ConditionNode = Class.new(_ConditionNode,
 	function(self, name, comparator, value)
 		self.name = name
diff --git a/standard/error.lua b/standard/error.lua
index da927d75e6d..18fe7125890 100644
--- a/standard/error.lua
+++ b/standard/error.lua
@@ -66,10 +66,7 @@ end)
 ---@param error Error
 ---@return boolean
 function Error.isError(error)
-	return type(error) == 'table'
-		and type(error.is_a) == 'function'
-		and error:is_a(Error)
-		and type(error.message) == 'string'
+	return Class.instanceOf(error, Error) and type(error.message) == 'string'
 end
 
 function Error:__tostring()
diff --git a/standard/links_stream.lua b/standard/links_stream.lua
index 33f97d41fa7..6da24c7a930 100644
--- a/standard/links_stream.lua
+++ b/standard/links_stream.lua
@@ -222,9 +222,7 @@ local StreamKey = Class.new(
 )
 StreamLinks.StreamKey = StreamKey
 
----@param tbl string
----@param languageCode string
----@param index integer
+---@overload fun(self, tbl: string, languageCode: string, index: integer): StreamKey
 ---@overload fun(self, tbl: StreamKey): StreamKey
 ---@overload fun(self, tbl: string): StreamKey
 function StreamKey:new(tbl, languageCode, index)
@@ -236,6 +234,7 @@ function StreamKey:new(tbl, languageCode, index)
 		index = tbl.index
 	-- All three parameters are supplied
 	elseif languageCode and index then
+		---@cast tbl -StreamKey
 		platform = tbl
 	elseif type(tbl) == 'string' then
 		local components = mw.text.split(tbl, '_', true)
@@ -251,8 +250,8 @@ function StreamKey:new(tbl, languageCode, index)
 		end
 	end
 
-	self.platform = platform --[[@as string]]
-	self.languageCode = languageCode --[[@as string]]
+	self.platform = platform
+	self.languageCode = languageCode
 	self.index = tonumber(index) --[[@as integer]]
 	self:_isValid()
 	self.languageCode = self.languageCode:lower()
@@ -298,14 +297,10 @@ function StreamKey:_isValid()
 	return true
 end
 
----@param value StreamKey
----@return true
+---@overload fun(value: StreamKey): true
 ---@overload fun(value: any): false
 function StreamKey._isStreamKey(value)
-	if type(value) == 'table' and type(value.is_a) == 'function' and value:is_a(StreamKey) then
-		return true
-	end
-	return false
+	return Class.instanceOf(value, StreamKey)
 end
 StreamKey.__tostring = StreamKey.toString
 
diff --git a/standard/result_or_error.lua b/standard/result_or_error.lua
index cac5c5cfaf5..0043a35d3e4 100644
--- a/standard/result_or_error.lua
+++ b/standard/result_or_error.lua
@@ -66,12 +66,12 @@ end
 
 ---@return boolean
 function ResultOrError:isResult()
-	return self:is_a(ResultOrError.Result)
+	return Class.instanceOf(self, ResultOrError.Result)
 end
 
 ---@return boolean
 function ResultOrError:isError()
-	return self:is_a(ResultOrError.Error)
+	return Class.instanceOf(self, ResultOrError.Error)
 end
 
 --[[
@@ -136,9 +136,7 @@ function ResultOrError.try(f, originalError)
 	xpcall(
 		function()
 			local result = f()
-			local isResultOrError = type(result) == 'table'
-				and type(result.is_a) == 'function'
-				and result:is_a(ResultOrError)
+			local isResultOrError = Class.instanceOf(result, ResultOrError)
 			resultOrError = isResultOrError
 				and result
 				or ResultOrError.Result(result)