Advanced Forceload
Kimapr

a better forceloading API

The Mob API
TX_Miner

Provides a simple API for mobs

VizLib
OgelGames

Visulization Library

CSMT Bots (Obsolete)
Logikí

Add bots to your game for training

Central Message
Wuzzy

Simple API to show messages to the center of the screen to players.

monster_api_gb
GigaByte

add an api to create bosses

Simple Models
AntumDeluge

Very simple models.

Minetest Systemd (API)
Piezo_

Debugging utility and compatibility tools for server owners and/or modpack creators

GetName
kevins

Adds an API and tool to generate random names for NPCs, mobs, and places.

Item Holders
Jose_ManuelS18

Adds 'Item Holders', blocks that hold your items in display, also provides a API.

Vision Lib
mt-mods

Common library for PolySaken's mods.

Object UUIDs
Silver Sandstone

Assigns a persistent UUID to every object.

Antigrief
sorcerykid

An API for validating node and item placement via a simple callback mechanism.

Interactive Item API
Jose_ManuelS18

Provides an API to make it easier to implement items' inner workings.

Compression Lib
The4spaceconstants

A library that provides functions to procedurally register compressed versions of nodes.

Keyevent
DS

Adds an event for when player presses a key.

NucleoTest
DarkXWolf17

Battle Royale-like game. Provides an API and a reference implementation. Highly radioactive. Work in progress.

NameGen
cronvel

Name generator API.

CentralAuth
1F616EMO

Player account unification across Luanti servers

Archipelago Library
Warr1024

Archipelago multi-world randomizer integration library

YL Ticker
AliasAlreadyTaken

Displays messages once per timeframe

FS51
Luke

Compatibility layer for formspecs

Grenades API
LandarVargan

Adds an API for easily creating grenades

flinv
Luke

API to add new inventory tabs which work across different inventory mods

Old Wizard Font
Pyrollo

OldWizard font for Font API

action queues
fluxionary

provides an API for queuing things for batch processing w/ various ways to specify the batch "size".

Player Settings
1F616EMO

Player-specific settings

Isogen
BuckarooBanzai

Generate isometric images from ingame builds

Discrete Player API
Hypernoot

A library for games which attaches players to node grid

AFK Indicator
1F616EMO

API to check player AFK status

Select Item
Wuzzy

Allows other mods to add a simple form to choose a single item.

description_monoids
fluxionary

API to allow multiple mods to make modifications to an itemstack's description

craftsystem
fluxionary

craft registration API which automatically deals w/ replacements

node entity queue
fluxionary

a queue for spreading out the generation of node entities over multiple server steps (smartshops, signs, itemframes, etc).

Debugging Console
sorcerykid

Provides an in-game HUD to easily monitor debug output

toolcap_monoids
fluxionary

an API to allow multiple sources to apply changes to a tools's capabilities.

Natural Entities
nurd3

A lightweight API for spawning random entities

Scripted World Editor
Neuromancer

API that allows you pass in scripting tables to fill a series of shapes of different sizes with different nodes

Bedrock Markup Language
sorcerykid

Bedrock Markup Language is an extensible markup language and API for formspecs.

Complete and Total Lua-Only Inventory Rewrite
Noodlemire

Creates a completely custom inventory system, which doesn't rely at all on any of the usual UserData objects.