API functions don't show completion snippet with lua_ls?

I’m running into a strange issue where certain builtin vim functions that are nested in nested tables don’t show a completion snippet, for example vim.keymap.set or vim.api.nvim_set_keymap show up in my autocompletion menu as merely functions without a completion snippet like the ones that exist for, for example, vim.tbl_deep_extend. Is this to be expected with lua-language-server? Is there any way to fix this?