About Minecraft commandsThe list starts from the Java Edition 26.1 command tree, the same structure the game uses to complete what you type with Tab. That is why the syntax does not depend on memory or on a tutorial: every argument, every alternative and every optional part comes from it. There are 86 commands and 5 aliases (/tp, /xp, /tell, /w and /tm), 91 names in total. The permission level, which commands only exist on a dedicated server, and the 59 gamerules were read from the official client.jar, while the descriptions and examples are our own text. Every example on the page was checked against the tree, so the line you copy has a form the game accepts.
Permission runs from 0 to 4. Level 0 works for any player (/help, /list, /msg, /me, /teammsg, /trigger and the /random roll). Level 2, the game operator level, covers 59 commands, among them /gamemode, /give, /tp, /time, /weather, /effect and /setblock; in a local world it needs cheats on. Level 3 is administration (/op, /ban, /whitelist, /kick, /tick), and level 4 belongs to the owner: /stop, /save-all and /publish. In a local world, /seed and /version work for everyone; on a dedicated server they need level 2.
The builder covers the 16 most used commands: /gamemode, /time, /weather, /difficulty, /gamerule, /tp, /effect, /xp, /kill, /summon, /setblock, /fill, /clear, /enchant, /spawnpoint (and /setworldspawn) and /title. It assembles the line as you choose, flags what is wrong, and includes a target selector builder (@e[type=zombie,distance=..10]). For /give and /tellraw, which have too many options for a simple form, the site has dedicated tools.