Everything Is Already an API

Ask the editor what it has

:lua =vim.fn.getcompletion('nvim_', 'function')
:lua =vim.fn.getcompletion('', 'option')
:lua =vim.fn.getcompletion('', 'command')

Three lists: every API function, every option, every Ex command. That is your whole surface.

Namespace	Is
`vim.api`	the raw editor — buffers, windows, marks, virtual text
`vim.fn`	every classic Vimscript function
`vim.opt` / `vim.o`	options, readable and writable while it runs
`vim.keymap`	mappings
`vim.lsp`, `vim.diagnostic`, `vim.treesitter`	the modern subsystems
`vim.uv`	timers, processes, file watching

:lua =vim.api.nvim_get_current_buf()

No plugin, no setup, nothing installed — it just answers.

A plugin is not a special kind of program. It is you, calling the same functions your config already calls.