Hi :)
I'm very impressed by Minetest, it's a great game (greatest open source game I've ever seen)! I decided to make some mods for it, but I haven't found any way to auto-complete Minetest's API functions in Eclipse. As I'm a big fan of Vim, I decided to make a Minetest API Completer plugin for Vim (my first vim plugin though). Here's the first version of it :)
The plugin uses pretty simple regexp heuristics to get information about API functions (function declaration + docs) from lua_api.txt, forms a list of them, which is used to propose completion. To open the completion list, you need to press Ctrl+X and then Ctrl+O (omni completion). Or you can use a plugin, that will open completion list as you type
Link to plugin's GitHub: https://github.com/DraggonFantasy/vim-minetest-api