Since the CommandAPI is used to register commands as a vanilla Minecraft command, you may want to use other plugins that are not written with the CommandAPI. For instance, if you want to include a command from a plugin which doesn't use the CommandAPI in a commandblock, (such as the /execute command), you can use the CommandAPI's command conversion system.

Developer's Note:

The command conversion system is nowhere near perfect. It tries its best to connect Bukkit plugins to vanilla Minecraft commands, but is not guaranteed to run flawlessly. If possible, consider forking/requesting a plugin and writing it with compatibility for the CommandAPI.

To register all commands that are declared by a plugin, the Converter.convert(Plugin) method can be used. This attempts to register all commands declared in a plugin's plugin.yml file, as well as any aliases or permissions stated in the plugin.yml file.

It is important to note that the plugin must be loaded before your plugin before attempting conversion. (Use loadbefore: [YourPlugin, CommandAPI] to ensure it loads before your plugin)

Say you have some plugin.yml file for a plugin.

name: myPlugin
main: some.random.package.Main
loadbefore: [CommandAPI]
version: 1.0
commands:
  gmc:
    aliases: gm1
  gms:
  i:
    permission: item.permission

Then, the following code will register the commands /gmc, /gm1, /gms and /i:

Converter.convert(Bukkit.getPluginManager().getPlugin("myPlugin"));

In addition to converting the whole plugin, the CommandAPI allows you to convert single commands at a time using the Converter.convert(Plugin, String) method, where the String argument refers to the command name as declared in the plugin's plugin.yml file.