Catspeak For Modders

Documentation for the Catspeak programming language is included in the Language Reference book.

Catspeak is a tool game developers can use to offer modding support to players. However, depending on the game, the modding API its developers reveal to modders could vary wildly. Because of this, you should contact the developers of the game and make sure they compile a list of which functions are exposed by their API, if they haven't already. Catspeak is not responsible for this.

The likelyhood that the modding API will include built-in GameMaker functions is high, so you should familiarise yourself with the documentation for the GameMaker standard library.

Catspeak comes packaged with a custom programming language which resembles JavaScript and GameMaker Language. It's likely that most games adding mod support through Catspeak will use this pre-packaged language. However, if the game you are creating a mod for uses a different language, then you need to ask the developers of that game for information about the language they are using for modding.

§ Dealing with Errorstop ^

Chances are your mod will fail or misbehave eventually. Whether or not this is a fatal error (the game crashes) or a silent error (the game unloads your mod) is up to the developers of the game to decide. If you suspect that your mod is failing for whatever reason, you should:

Figure out how the developers are handling mod errors so you can get a an error trace. This will help tell you the line and column the error occurred on.
Check that your code does not have any typos, which can be a common error.
Check that the syntax for your code is correct by familiarising yourself with the modding language. Documentation for the built-in Catspeak programming language can be found in the Language Reference book. When in doubt, do not make assumptions about syntax; look it up.
Ask the developers for more debugging tools, like exposing GameMakers show_debug_message function.
Cry in a corner against all odds.