diff --git a/lua/input/config.lua b/lua/input/config.lua
index 3c825e3..a65a3a3 100644
--- a/lua/input/config.lua
+++ b/lua/input/config.lua
@@ -1,17 +1,18 @@
-local config = {}
-
 ---@class input.width_options
 ---@field prefer number
 ---@field min_value number[]
 ---@field max_value number[]
 
----@class input.options
+---@class input.config
 ---@field icon string
 ---@field default_prompt string
 ---@field win_options vim.wo
 ---@field buf_options vim.bo
 ---@field win_config vim.api.keyset.win_config
 ---@field width_options input.width_options
+local config = {}
+
+---@type input.config
 local defaults = {
     icon = "",
     default_prompt = "Input",
@@ -45,11 +46,10 @@ local defaults = {
     },
 }
 
----@type input.options
 local options = vim.deepcopy(defaults)
 
 ---Extend default with user's config.
----@param opts input.options
+---@param opts input.config
 function config.extend(opts)
     if not opts or vim.tbl_isempty(opts) then
         return
diff --git a/lua/input/init.lua b/lua/input/init.lua
index a462cb2..c117365 100644
--- a/lua/input/init.lua
+++ b/lua/input/init.lua
@@ -1,6 +1,10 @@
 local M = {}
 
+---@param opts? vim.ui.input.Opts
+---@param on_confirm fun(input?: string)
 local function input(opts, on_confirm)
+    opts = (opts and not vim.tbl_isempty(opts)) and opts or vim.empty_dict()
+
     local config = require "input.config"
     local utils = require "input.utils"
     local win_config = config.win_config
diff --git a/lua/input/utils.lua b/lua/input/utils.lua
index 452a512..c717629 100644
--- a/lua/input/utils.lua
+++ b/lua/input/utils.lua
@@ -1,6 +1,9 @@
 ---Thanks: https://github.com/stevearc/dressing.nvim/blob/master/lua/dressing/util.lua
 local M = {}
 
+---@param value number
+---@param max_value number
+---@return number
 local function calculate_float(value, max_value)
     if value then
         local _, p = math.modf(value)
@@ -13,6 +16,11 @@ local function calculate_float(value, max_value)
     return value
 end
 
+---@param value number[]
+---@param max_value number
+---@param aggregator fun(x: number, ...: number)
+---@param limit number
+---@return number
 local function calculate_list(value, max_value, aggregator, limit)
     local result = limit
 
@@ -23,6 +31,9 @@ local function calculate_list(value, max_value, aggregator, limit)
     return result
 end
 
+---@param relative "cursor"|"editor"|"laststatus"|"mouse"|"tabline"|"win"
+---@param winid? integer
+---@return integer
 local function get_max_width(relative, winid)
     return relative == "editor" and vim.o.columns or vim.api.nvim_win_get_width(winid or 0)
 end
@@ -48,7 +59,7 @@ local function calculate_size(current_size, size_options, total_size)
 end
 
 ---Calculate width.
----@param relative "cursor"|"editor"
+---@param relative "cursor"|"editor"|"laststatus"|"mouse"|"tabline"|"win"
 ---@param current_size number
 ---@param width_options input.width_options
 ---@return integer
@@ -57,7 +68,7 @@ function M.calculate_width(relative, current_size, width_options)
 end
 
 ---Get max string width.
----@param lines table<string>
+---@param lines string[]
 ---@return integer
 function M.get_max_strwidth(lines)
     local max = 0