docs: Reword details regarding symbols.icon_fetcher

README.md

@@ -391,13 +391,14 @@ Pass a table to the setup call with your configuration options.
     -- You can use a custom function that returns the icon for each symbol kind.
     -- This function takes a kind (string) as parameter and should return an
     -- icon as string.
-    ---@param kind string
+    ---@param kind string Key of the icons table below
     ---@param bufnr integer Code buffer
-    ---@returns string|boolean The icon string (key of `icons` table), or `false`
+    ---@returns string|boolean The icon string to display, such as "f", or `false`
     ---                        to fallback to `icon_source`.
     icon_fetcher = nil,
-    -- 3rd party source for fetching icons. Fallback if icon_fetcher returned
-    -- empty string. Currently supported values: 'lspkind'
+    -- 3rd party source for fetching icons. This is used as a fallback if
+    -- icon_fetcher returned an empty string.
+    -- Currently supported values: 'lspkind'
     icon_source = nil,
     -- The next fallback if both icon_fetcher and icon_source has failed, is
     -- the custom mapping of icons specified below. The icons table is also

lua/outline/symbols.lua

@@ -47,6 +47,7 @@ end
 
 ---@param kind string|integer
 ---@param bufnr integer
+---@return string icon
 function M.icon_from_kind(kind, bufnr)
   local kindstr = kind
   if type(kind) ~= 'string' then