diff --git a/runtime/lua/tohtml.lua b/runtime/lua/tohtml.lua
index 5e145950b7..120247ed4e 100644
--- a/runtime/lua/tohtml.lua
+++ b/runtime/lua/tohtml.lua
@@ -65,9 +65,7 @@ local function notify(msg)
   if #notifications == 0 then
     vim.schedule(function()
       if #notifications > 1 then
-        vim.notify(
-          ('TOhtml: %s (+ %d more warnings)'):format(notifications[1], tostring(#notifications - 1))
-        )
+        vim.notify(('TOhtml: %s (+ %d more warnings)'):format(notifications[1], #notifications - 1))
       elseif #notifications == 1 then
         vim.notify('TOhtml: ' .. notifications[1])
       end
diff --git a/runtime/lua/vim/_meta.lua b/runtime/lua/vim/_meta.lua
index 731dd5b923..c9f207cb20 100644
--- a/runtime/lua/vim/_meta.lua
+++ b/runtime/lua/vim/_meta.lua
@@ -34,3 +34,5 @@ vim.uri_from_fname = uri.uri_from_fname
 vim.uri_from_bufnr = uri.uri_from_bufnr
 vim.uri_to_fname = uri.uri_to_fname
 vim.uri_to_bufnr = uri.uri_to_bufnr
+
+vim.provider = require('vim.provider')
diff --git a/runtime/lua/vim/_meta/vimfn.lua b/runtime/lua/vim/_meta/vimfn.lua
index f256f63768..84bb26a135 100644
--- a/runtime/lua/vim/_meta/vimfn.lua
+++ b/runtime/lua/vim/_meta/vimfn.lua
@@ -1642,7 +1642,7 @@ function vim.fn.execute(command, silent) end
 --- If {expr} starts with "./" the |current-directory| is used.
 ---
 --- @param expr any
---- @return any
+--- @return string
 function vim.fn.exepath(expr) end
 
 --- The result is a Number, which is |TRUE| if {expr} is
diff --git a/runtime/lua/vim/deprecated/health.lua b/runtime/lua/vim/deprecated/health.lua
index 0f6b1f578c..64a755b248 100644
--- a/runtime/lua/vim/deprecated/health.lua
+++ b/runtime/lua/vim/deprecated/health.lua
@@ -1,7 +1,7 @@
 local M = {}
 local health = vim.health
 
-local deprecated = {}
+local deprecated = {} ---@type {[1]: string, [2]: table, [3]: string}[]
 
 function M.check()
   if next(deprecated) == nil then
diff --git a/runtime/lua/vim/health.lua b/runtime/lua/vim/health.lua
index afeba2ee9d..236f9da752 100644
--- a/runtime/lua/vim/health.lua
+++ b/runtime/lua/vim/health.lua
@@ -104,10 +104,10 @@ local function filepath_to_healthcheck(path)
     local subpath = path:gsub('.*lua/', '')
     if vim.fs.basename(subpath) == 'health.lua' then
       -- */health.lua
-      name = assert(vim.fs.dirname(subpath))
+      name = vim.fs.dirname(subpath)
     else
       -- */health/init.lua
-      name = assert(vim.fs.dirname(assert(vim.fs.dirname(subpath))))
+      name = vim.fs.dirname(vim.fs.dirname(subpath))
     end
     name = name:gsub('/', '.')
 
@@ -301,11 +301,13 @@ end
 local PATTERNS = { '/autoload/health/*.vim', '/lua/**/**/health.lua', '/lua/**/**/health/init.lua' }
 --- :checkhealth completion function used by cmdexpand.c get_healthcheck_names()
 M._complete = function()
-  local unique = vim
+  local unique = vim ---@type table<string,boolean>
+    ---@param pattern string
     .iter(vim.tbl_map(function(pattern)
       return vim.tbl_map(path2name, vim.api.nvim_get_runtime_file(pattern, true))
     end, PATTERNS))
     :flatten()
+    ---@param t table<string,boolean>
     :fold({}, function(t, name)
       t[name] = true -- Remove duplicates
       return t
@@ -364,7 +366,7 @@ function M._check(mods, plugin_names)
       vim.fn.call(func, {})
     else
       local f = assert(loadstring(func))
-      local ok, output = pcall(f)
+      local ok, output = pcall(f) ---@type boolean, string
       if not ok then
         M.error(
           string.format('Failed to run healthcheck for "%s" plugin. Exception:\n%s\n', name, output)
@@ -391,7 +393,7 @@ function M._check(mods, plugin_names)
     end
     s_output[#s_output + 1] = ''
     s_output = vim.list_extend(header, s_output)
-    vim.fn.append('$', s_output)
+    vim.fn.append(vim.fn.line('$'), s_output)
     vim.cmd.redraw()
   end
 
diff --git a/runtime/lua/vim/health/health.lua b/runtime/lua/vim/health/health.lua
index 5bc03199ee..235dacb82a 100644
--- a/runtime/lua/vim/health/health.lua
+++ b/runtime/lua/vim/health/health.lua
@@ -239,6 +239,7 @@ local function check_tmux()
     return
   end
 
+  ---@param option string
   local get_tmux_option = function(option)
     local cmd = 'tmux show-option -qvg ' .. option -- try global scope
     local out = vim.fn.system(vim.fn.split(cmd))
@@ -378,7 +379,7 @@ local function check_terminal()
     'SSH_TTY',
   }) do
     if vim.env[env_var] then
-      health.info(vim.fn.printf('$%s="%s"', env_var, vim.env[env_var]))
+      health.info(string.format('$%s="%s"', env_var, vim.env[env_var]))
     end
   end
 end
diff --git a/runtime/lua/vim/lsp/util.lua b/runtime/lua/vim/lsp/util.lua
index 5a229a1169..0099e82f52 100644
--- a/runtime/lua/vim/lsp/util.lua
+++ b/runtime/lua/vim/lsp/util.lua
@@ -616,7 +616,7 @@ function M.rename(old_fname, new_fname, opts)
     buf_rename[b] = { from = old_bname, to = new_bname }
   end
 
-  local newdir = assert(vim.fs.dirname(new_fname))
+  local newdir = vim.fs.dirname(new_fname)
   vim.fn.mkdir(newdir, 'p')
 
   local ok, err = os.rename(old_fname_full, new_fname)
@@ -625,7 +625,7 @@ function M.rename(old_fname, new_fname, opts)
   local old_undofile = vim.fn.undofile(old_fname_full)
   if uv.fs_stat(old_undofile) ~= nil then
     local new_undofile = vim.fn.undofile(new_fname)
-    vim.fn.mkdir(assert(vim.fs.dirname(new_undofile)), 'p')
+    vim.fn.mkdir(vim.fs.dirname(new_undofile), 'p')
     os.rename(old_undofile, new_undofile)
   end
 
diff --git a/runtime/lua/vim/provider/health.lua b/runtime/lua/vim/provider/health.lua
index d6932f651e..fa2c452268 100644
--- a/runtime/lua/vim/provider/health.lua
+++ b/runtime/lua/vim/provider/health.lua
@@ -95,10 +95,10 @@ local function system(cmd, args)
     error(emsg)
   end
 
-  -- return opts.output
   return vim.trim(vim.fn.system(cmd)), shell_error_code
 end
 
+---@param provider string
 local function provider_disabled(provider)
   local loaded_var = 'loaded_' .. provider .. '_provider'
   local v = vim.g[loaded_var]
@@ -126,9 +126,9 @@ local function clipboard()
     health.error('pbcopy does not work with tmux version: ' .. tmux_version, advice)
   end
 
-  local clipboard_tool = vim.fn['provider#clipboard#Executable']()
+  local clipboard_tool = vim.fn['provider#clipboard#Executable']() ---@type string
   if vim.g.clipboard ~= nil and clipboard_tool == '' then
-    local error_message = vim.fn['provider#clipboard#Error']()
+    local error_message = vim.fn['provider#clipboard#Error']() ---@type string
     health.error(
       error_message,
       "Use the example in :help g:clipboard as a template, or don't set g:clipboard at all."
@@ -179,7 +179,7 @@ local function node()
     )
   end
 
-  local node_detect_table = vim.fn['provider#node#Detect']()
+  local node_detect_table = vim.fn['provider#node#Detect']() ---@type string[]
   local host = node_detect_table[1]
   if host:find('^%s*$') then
     health.warn('Missing "neovim" npm (or yarn, pnpm) package.', {
@@ -290,7 +290,7 @@ local function perl()
   elseif latest_cpan[1] == '!' then
     local cpanm_errs = vim.split(latest_cpan, '!')
     if cpanm_errs[1]:find("Can't write to ") then
-      local advice = {}
+      local advice = {} ---@type string[]
       for i = 2, #cpanm_errs do
         advice[#advice + 1] = cpanm_errs[i]
       end
@@ -303,7 +303,7 @@ local function perl()
       return
     end
   end
-  latest_cpan = vim.fn.matchstr(latest_cpan, [[\(\.\?\d\)\+]])
+  latest_cpan = tostring(vim.fn.matchstr(latest_cpan, [[\(\.\?\d\)\+]]))
   if latest_cpan:find('^%s*$') then
     health.error('Cannot parse version number from cpanm output: ' .. latest_cpan)
     return
@@ -349,9 +349,11 @@ local function python_exepath(invocation)
   return vim.fs.normalize(vim.trim(p.stdout))
 end
 
--- Check if pyenv is available and a valid pyenv root can be found, then return
--- their respective paths. If either of those is invalid, return two empty
--- strings, effectively ignoring pyenv.
+--- Check if pyenv is available and a valid pyenv root can be found, then return
+--- their respective paths. If either of those is invalid, return two empty
+--- strings, effectively ignoring pyenv.
+---
+--- @return {[1]: string, [2]: string}
 local function check_for_pyenv()
   local pyenv_path = vim.fn.resolve(vim.fn.exepath('pyenv'))
 
@@ -394,7 +396,9 @@ local function check_bin(bin)
   return true
 end
 
--- Fetch the contents of a URL.
+--- Fetch the contents of a URL.
+---
+--- @param url string
 local function download(url)
   local has_curl = vim.fn.executable('curl') == 1
   if has_curl and vim.fn.system({ 'curl', '-V' }):find('Protocols:.*https') then
@@ -429,25 +433,24 @@ local function download(url)
   return message
 end
 
--- Get the latest Nvim Python client (pynvim) version from PyPI.
+--- Get the latest Nvim Python client (pynvim) version from PyPI.
 local function latest_pypi_version()
   local pypi_version = 'unable to get pypi response'
   local pypi_response = download('https://pypi.python.org/pypi/pynvim/json')
   if pypi_response ~= '' then
     local pcall_ok, output = pcall(vim.fn.json_decode, pypi_response)
-    local pypi_data
-    if pcall_ok then
-      pypi_data = output
-    else
+    if not pcall_ok then
       return 'error: ' .. pypi_response
     end
 
+    local pypi_data = output
     local pypi_element = pypi_data['info'] or {}
     pypi_version = pypi_element['version'] or 'unable to parse'
   end
   return pypi_version
 end
 
+--- @param s string
 local function is_bad_response(s)
   local lower = s:lower()
   return vim.startswith(lower, 'unable')
@@ -455,16 +458,18 @@ local function is_bad_response(s)
     or vim.startswith(lower, 'outdated')
 end
 
--- Get version information using the specified interpreter.  The interpreter is
--- used directly in case breaking changes were introduced since the last time
--- Nvim's Python client was updated.
---
--- Returns: {
---     {python executable version},
---     {current nvim version},
---     {current pypi nvim status},
---     {installed version status}
--- }
+--- Get version information using the specified interpreter.  The interpreter is
+--- used directly in case breaking changes were introduced since the last time
+--- Nvim's Python client was updated.
+---
+--- @param python string
+---
+--- Returns: {
+---     {python executable version},
+---     {current nvim version},
+---     {current pypi nvim status},
+---     {installed version status}
+--- }
 local function version_info(python)
   local pypi_version = latest_pypi_version()
 
@@ -512,9 +517,9 @@ local function version_info(python)
   if rc ~= 0 or nvim_version == '' then
     nvim_version = 'unable to find pynvim module version'
     local base = vim.fs.basename(nvim_path)
-    local metas = vim.fn.glob(base .. '-*/METADATA', 1, 1)
-    vim.list_extend(metas, vim.fn.glob(base .. '-*/PKG-INFO', 1, 1))
-    vim.list_extend(metas, vim.fn.glob(base .. '.egg-info/PKG-INFO', 1, 1))
+    local metas = vim.fn.glob(base .. '-*/METADATA', true, 1)
+    vim.list_extend(metas, vim.fn.glob(base .. '-*/PKG-INFO', true, 1))
+    vim.list_extend(metas, vim.fn.glob(base .. '.egg-info/PKG-INFO', true, 1))
     metas = table.sort(metas, compare)
 
     if metas and next(metas) ~= nil then
@@ -544,14 +549,13 @@ end
 local function python()
   health.start('Python 3 provider (optional)')
 
-  local pyname = 'python3' ---@type string?
   local python_exe = ''
   local virtual_env = os.getenv('VIRTUAL_ENV')
   local venv = virtual_env and vim.fn.resolve(virtual_env) or ''
-  local host_prog_var = pyname .. '_host_prog'
-  local python_multiple = {}
+  local host_prog_var = 'python3_host_prog'
+  local python_multiple = {} ---@type string[]
 
-  if provider_disabled(pyname) then
+  if provider_disabled('python3') then
     return
   end
 
@@ -564,8 +568,7 @@ local function python()
     health.info(message)
   end
 
-  local pythonx_warnings
-  pyname, pythonx_warnings = vim.provider.python.detect_by_module('neovim')
+  local pyname, pythonx_warnings = vim.provider.python.detect_by_module('neovim')
 
   if not pyname then
     health.warn(
@@ -653,12 +656,7 @@ local function python()
       )
       health.warn('pyenv is not set up optimally.', advice)
     elseif venv ~= '' then
-      local venv_root
-      if pyenv_root ~= '' then
-        venv_root = pyenv_root
-      else
-        venv_root = vim.fs.dirname(venv)
-      end
+      local venv_root = pyenv_root ~= '' and pyenv_root or vim.fs.dirname(venv)
 
       if vim.startswith(vim.fn.resolve(python_exe), venv_root .. '/') then
         local advice = string.format(
@@ -743,9 +741,9 @@ local function python()
     health.ok('no $VIRTUAL_ENV')
     return
   end
-  local errors = {}
+  local errors = {} ---@type string[]
   -- Keep hints as dict keys in order to discard duplicates.
-  local hints = {}
+  local hints = {} ---@type table<string, boolean>
   -- The virtualenv should contain some Python executables, and those
   -- executables should be first both on Nvim's $PATH and the $PATH of
   -- subshells launched from Nvim.
diff --git a/scripts/gen_help_html.lua b/scripts/gen_help_html.lua
index e238fee5f8..722efc489f 100644
--- a/scripts/gen_help_html.lua
+++ b/scripts/gen_help_html.lua
@@ -1372,7 +1372,7 @@ function M.validate(help_dir, include, parser_path)
   parser_path = parser_path and vim.fn.expand(parser_path) or nil
 
   for _, f in ipairs(helpfiles) do
-    local helpfile = assert(vim.fs.basename(f))
+    local helpfile = vim.fs.basename(f)
     local rv = validate_one(f, parser_path)
     print(('validated (%-4s errors): %s'):format(#rv.parse_errors, helpfile))
     if #rv.parse_errors > 0 then
@@ -1430,7 +1430,7 @@ end
 ---    :help files, we can be precise about the tolerances here.
 --- @param help_dir? string e.g. '$VIMRUNTIME/doc' or './runtime/doc'
 function M.test_gen(help_dir)
-  local tmpdir = assert(vim.fs.dirname(vim.fn.tempname()))
+  local tmpdir = vim.fs.dirname(vim.fn.tempname())
   help_dir = vim.fn.expand(help_dir or '$VIMRUNTIME/doc')
   print('doc path = ' .. vim.uv.fs_realpath(help_dir))
 
diff --git a/scripts/gen_vimdoc.lua b/scripts/gen_vimdoc.lua
index 9c6225efc3..b88bdff99b 100755
--- a/scripts/gen_vimdoc.lua
+++ b/scripts/gen_vimdoc.lua
@@ -813,7 +813,7 @@ local function get_script_path()
 end
 
 local script_path = get_script_path()
-local base_dir = vim.fs.dirname(assert(vim.fs.dirname(script_path)))
+local base_dir = vim.fs.dirname(vim.fs.dirname(script_path))
 
 local function delete_lines_below(doc_file, tokenstr)
   local lines = {} --- @type string[]
@@ -965,7 +965,7 @@ local function gen_target(cfg)
       end
     end
     -- FIXME: Using f_base will confuse `_meta/protocol.lua` with `protocol.lua`
-    local f_base = assert(vim.fs.basename(f))
+    local f_base = vim.fs.basename(f)
     sections[f_base] = make_section(f_base, cfg, briefs_txt, funs_txt)
   end
 
diff --git a/scripts/luacats_parser.lua b/scripts/luacats_parser.lua
index cb301b32e4..66fe8ed616 100644
--- a/scripts/luacats_parser.lua
+++ b/scripts/luacats_parser.lua
@@ -458,7 +458,7 @@ local function dump_uncommitted(filename, uncommitted)
   local out_path = 'luacats-uncommited/' .. filename:gsub('/', '%%') .. '.txt'
   if #uncommitted > 0 then
     print(string.format('Could not commit %d objects in %s', #uncommitted, filename))
-    vim.fn.mkdir(assert(vim.fs.dirname(out_path)), 'p')
+    vim.fn.mkdir(vim.fs.dirname(out_path), 'p')
     local f = assert(io.open(out_path, 'w'))
     for i, x in ipairs(uncommitted) do
       f:write(i)
diff --git a/src/nvim/eval.lua b/src/nvim/eval.lua
index f0c8963459..ceaba11f41 100644
--- a/src/nvim/eval.lua
+++ b/src/nvim/eval.lua
@@ -2133,6 +2133,7 @@ M.funcs = {
     name = 'exepath',
     params = { { 'expr', 'any' } },
     signature = 'exepath({expr})',
+    returns = 'string',
   },
   exists = {
     args = 1,