Launcher API

Overview

Every page of the launcher has a command, and every command but three has an MCP tool with the same arguments; a tool runs the command with --json. Tools that change the player's things for good need confirm: true; with No AI on, the MCP server is off.

Guide

1. horizon-launcher versions, horizon-launcher install latest, horizon-launcher play.
2. Modpacks: horizon-launcher modpack import <file>, then modpack port and modpack play (modpacks.md).
3. For an agent: horizon-launcher agent-config prints how to connect a client to horizon-launcher mcp.

Reference

launcher-commands.md, generated from launcher/src/cli.rs: every command, its arguments and its MCP tool.

Examples

horizon-launcher versions --installed --json
horizon-launcher mods search minimap --kind mod --json
horizon-launcher servers create --name "Weekend" --player Alex --json

Stability

Preview (stability.md): command names, arguments and MCP tool names are the contract; --json output shapes are not yet described in the reference.

Not there yet

• A Horizon modpack manifest. A pack made for Horizon (not a port of a Java pack) needs its own file: the pack's id, name and version; the Horizon API lines and the release line it needs; its .hmod mods (id, version, SHA-256, where to download it, client, server or both); resource packs; default settings; and whether it has a server side. One manifest serves the launcher, horizon-server (a server installs the server side of the same pack) and the mod browser. Designed from what a pack maker does, versioned per stability.md, with a schema test.
• JSON output schemas for every command, in the generated reference, so MCP tools declare their output.
• A version in MCP serverInfo and --json output, as for agent control.
• Compatibility tests: golden --json output per command.

Changelog

• Unversioned so far: the command table and the generated reference are the contract.