The GMCP protocol definition can be found at: https://tintin.mudhalla.net/protocols/gmcp/

GMCP packets consist of a command (package) and a json document with arguments or parameters. The base protocol defines only the Core package, and leaves others to emergence in the community.

Internal GMCP Packages:

Core

Core.Hello
Core.Supports.Set [string, string, ...]
Core.Supports.Add [string, string, ...]
Core.Supports.Remove [string, string, ...]

This is the basic package that all GMCP implementors must respect. It negotiates what packages are available in common between the client and server. Each string in the arguments above is the name of a package followed by a space and its version number.

Client.Media

Client.Media.Load {name|file: ,tag: ,url: }
Client.Media.Play {name|file: ,tag: ,type: ,url: ,volume: ,loops: ,priority: }
Client.Media.Stop {name|file: ,tag: ,type: }

This module is for caching, playing, and stopping audio or video type media. Only the audio media is supported at present.

Client.Login

Client.Login.Default {type: "password-credentials"}
Client.Login.Response {user: ,password: }
Client.Login.Credentials {name|file: ,tag: ,type: }

This module is logging into a server with credentials. The type of credentials is sent by the server using the Default command, and the client sends those credentials using Credentials, to which the server responds with Response.