Document LaTeX \usepackage lines with CTAN caption in Vim. Requires one package per line.

#Sample output

\usepackage{fancyhdr} % Extensive control of page headers and footers in LaTeX2e
\usepackage{enumitem} % Control layout of itemize, enumerate, description
\usepackage{multicol} % Intermix single and multiple columns
\usepackage{multirow} % Create tabular cells spanning multiple rows
\usepackage{mathtools} % Mathematical tools to use with amsmath
\usepackage{amsthm} % Typesetting theorems (AMS style)
\usepackage{amssymb} % 
\usepackage{amsfonts} % TeX fonts from the American Mathematical Society
\usepackage{graphicx} % Enhanced support for graphics

.vimrc

" Add descriptions to tex usepackage lines
function! Texdesc()
    %s/^\\usepackage\(\[[a-zA-Z0-9_,-]*\]\)\={\([a-zA-Z0-9_-]\+\)}$/\=submatch(0) . ' % ' .substitute(system("~\/.local\/bin\/texdesc.sh ".submatch(2)), "\n", "", "")/g
endfunction
command! Texdesc call Texdesc() 

texdesc.sh

#!/bin/sh
# Check if ctan package list exists
if  [ ! -e ~/.ctan_package_list ]; then
    curl -s --output ~/.ctan_package_list https://ctan.org/json/1.3/packages
fi
# Check if older than 15 days
if test "$(find ~/.ctan_package_list -mtime +15)"; then
    curl -s --output ~/.ctan_package_list https://ctan.org/json/1.3/packages
fi
# Find caption for matching package name
jq --raw-output '.[] | select(.name | match("^'$1'$"))| .caption' ~/.ctan_package_list