When using the Steam API, this function can be called to check that the Steam client API has been initialised correctly before any doing any further calls to Steam specific functions in your game.
global.steam_api = false;
if steam_stats_ready() && steam_is_overlay_enabled()
global.steam_api = true;
The above code will set a global variable to true if the Steam client API is correctly initialised, along with the Steam statistics and overlay functionality, or it will set the variable to false otherwise.