Examples

The four plugins in the Ready Up repo, and which parts of the SDK each one shows.

Every plugin in the ready-up repo uses the same SDK you do. None of them has special access to the core. Read them as real-world references.

hello

plugins/hello/hello.c. Plain C, about 200 lines. Start here.

Chat and console commands, an ru hello subcommand, a hidden chat command, and a console command it only watches.
A tick heartbeat, and a frame counter that also runs when the server does not simulate.
Lifecycle events, player_death as a raw engine event, and a count of log lines.
A greeting setting read with config_get.
A load counter kept across ru plugin reload hello with the stash.
Publishes its own interface, readyup.hello.v1.
Asks for API 1.0 and checks every newer function with RU_API_HAS, so it loads on older cores too.

plugins/skins/. C++. Applies weapon paints, knives, gloves and agents.

Entities and schema: walks player controllers to pawns to weapons with entity_by_index, entity_from_handle and schema_offset. Keeps entity handles across frames, never pointers.
Item attributes, knife subclass, models and bodygroups, then entity_mark_changed so clients get the change.
A gamedata fragment, engine-surface.skins.json. The signatures only skins needs ship with skins, not with the core.
A worker thread for file reads, started in load and joined in unload. The game thread only reads an in-memory cache.
Raw engine events to prefetch loadouts on spawn and pickup, and to count StatTrak kills.
Fleet handlers (skins.loadout) and a capability (skins.v1), looked up through readyup.fleet.v1 on every tick.

plugins/match/. C++, the largest plugin. The whole match flow.

Many chat commands, some hidden with RU_CMD_HIDE, and every ru <x> subcommand the match flow has.
Lifecycle events and server log lines. The knife round works from log lines alone.
Per-player center HTML for the ready panel and the welcome card.
set_round_termination_suppressed for warmup and practice, set_chat_name_prefix for admins and captains.
An admin provider (set_admin_provider) that answers for the whole server.
Its own settings from readyup.cfg, [match] and cfg/ReadyUp/match.cfg, and JSON data files in its data folder.
Publishes readyup.match.v1 for the core's /status, and its own ru selftest lines.
Keeps a running match across ru plugin reload match with the stash. See What survives a reload.
Uses readyup.fleet.v1 to take match assignments and stream state to the platform.
match_host_test loads the real match.so into the plugin host without a server.

plugins/fleet/. C++. The link to the Auto Tournament platform.

A network thread (libcurl WebSockets) that never blocks the game thread. Messages reach other plugins through post_to_game_thread.
Publishes readyup.fleet.v1 with thread-safe members, for the core and other plugins.
Handles its own reload: every other plugin compares instance_id() and registers its handlers again.
Keeps a value in the stash across reloads.
Its own ru selftest lines.
Unit tests, and an integration test against a mock platform.

You want to	Look at
Add a chat or console command	`hello.c`
Show something in the middle of the screen	`plugins/match/readyup/ready_hud.cpp`
Change something on a player or weapon	`plugins/skins/apply.cpp`, `cosmetics.cpp`
Run work off the game thread	`plugins/skins/loadout.cpp`, `plugins/fleet/fleet_client.cpp`
Keep state across a reload	`hello.c` (small), `plugins/match/readyup/reload_state.cpp` (large)
Publish an interface	`hello.c`, `plugins/match/readyup/match_plugin.cpp` (with `match_status.cpp`)
Add `ru selftest` lines	`plugins/fleet/fleet_plugin.cpp`