ilo

A programming language AI agents write, not humans. Named from Toki Pona for "tool".

Python                                    ilo
─────                                     ───
def total(price, quantity, rate):          tot p:n q:n r:n>n;s=*p q;t=*s r;+s t
    sub = price * quantity
    tax = sub * rate
    return sub + tax

4 lines, 30 tokens, 90 chars              1 line, 10 tokens, 20 chars

0.33× the tokens. 0.22× the characters. Same semantics. Type-verified before execution.

Why

AI agents pay three costs per program: generation tokens, error feedback, retries. ilo cuts all three:

• Shorter programs - prefix notation eliminates parentheses; positional args eliminate boilerplate
• Verified first - type errors caught before execution; agents get ILO-T004 not a stack trace
• Compact errors - one token, not a paragraph; agents correct faster, fewer retries

Install

macOS / Linux

curl -fsSL https://raw.githubusercontent.com/ilo-lang/ilo/main/install.sh | sh

Windows (PowerShell)

Invoke-WebRequest -Uri https://github.com/ilo-lang/ilo/releases/latest/download/ilo-x86_64-pc-windows-msvc.exe -OutFile ilo.exe

npm (any platform with Node 20+)

npm i -g ilo-lang

# or run without installing
npx ilo-lang 'dbl x:n>n;*x 2' 5

WASM mode: interpreter only. HTTP builtins (get, $, post) require the native binary.

Rust

cargo install ilo

Agent-specific install

Agent	Install
Claude Code	/plugin marketplace add ilo-lang/ilo then /plugin install ilo-lang/ilo
Claude Cowork	Browse Plugins → Add marketplace → ilo-lang/ilo → install
Other agents	Copy skills/ilo/ into your agent's skills directory

All install methods →

Quick start

# Inline
ilo 'dbl x:n>n;*x 2' 5                    # → 10

# From file
ilo program.ilo functionName arg1 arg2

Tutorial: Write your first program →

What it looks like

Guards - flat, no nesting:

cls sp:n>t;>=sp 1000 "gold";>=sp 500 "silver";"bronze"

Pipes - left-to-right composition:

run x:n>n;x>>dbl>>inc

Data pipeline - fetch, parse, filter, sum:

fetch url:t>R ? t;r=($!url);rdb! r "json"
proc rows:L ?>n;clean=flt pos rows;sum clean
pos x:?>b;>x 0

Auto-unwrap ! - eliminates Result matching:

ilo 'inner x:n>R n t;~x  outer x:n>R n t;~(inner! x)' 42  # → 42

Teaching agents

ilo ships as an Agent Skill. Install the plugin and the agent learns ilo automatically.

For manual context loading:

ilo -ai              # compact spec for LLM system prompts
ilo help lang        # full spec

Key docs

Introduction	What ilo is and why
Installation	All install methods
Tutorial	Write your first program
Types & Functions	Core language guide
Prefix Notation	Why prefix saves tokens
Guards	Pattern matching without if/else
Pipes	Function composition
Collections	Lists and higher-order functions
Error Handling	Result types and auto-unwrap
Data & I/O	HTTP, files, JSON, env
MCP Integration	Connect MCP servers
CLI Reference	Flags, REPL, output modes
Builtins	All built-in functions
Error Codes	ILO-XXXX reference
SPEC.md	Full language specification
examples/	Runnable examples (also test suite)

Benchmarks

Per-call time (ns) across 8 micro-benchmarks. Lower is better. Full results →

Language	numeric	string	record	mixed	guards	recurse	foreach	while	pipe	file	api
Rust (native)	496ns	3.7us	n/a	9.9us	1.8us	18.8us	44ns	n/a	254ns	9.3us	159.0us
Go	705ns	17.2us	107ns	6.2us	738ns	21.5us	162ns	30ns	31ns	19.0us	200.0us
C# (.NET)	6.2us	14.6us	554ns	29.9us	6.8us	24.7us	1.2us	417ns	610ns	22.7us	228.8us
Kotlin (JVM)	492ns	8.2us	265ns	7.8us	1.0us	17.4us	1.2us	168ns	226ns	18.6us	183.4us
LuaJIT	513ns	19.0us	149ns	9.8us	3.5us	28.7us	676ns	48ns	85ns	14.7us	63.2us
Node/V8	569ns	1.3us	354ns	5.3us	1.0us	46.7us	480ns	81ns	191ns	12.4us	284.5us
TypeScript	427ns	1.2us	236ns	5.4us	1.0us	45.9us	421ns	75ns	167ns	12.7us	310.2us
ilo AOT	1.8us	12.9us	1.1us	33.0us	5.3us	37.3us	1.1us	148ns	126ns	n/a	n/a
ilo JIT	1.3us	5.0us	504ns	26.2us	3.2us	37.2us	935ns	150ns	125ns	16.5us	1.7ms
ilo VM	11.3us	10.5us	3.1us	31.6us	53.5us	528.3us	2.4us	1.2us	7.0us	16.9us	171.1us
ilo Interpreter	91.4us	61.2us	54.3us	1.3ms	1.0ms	17.4ms	84.2us	10.6us	155.1us	32.3us	174.7us
Lua	4.0us	39.8us	7.5us	49.2us	27.0us	339.1us	3.8us	967ns	4.3us	16.1us	54.3us
Ruby	19.8us	26.0us	8.7us	18.4us	38.5us	373.0us	3.2us	2.3us	6.3us	19.6us	269.2us
PHP	6.4us	4.0us	4.0us	8.2us	25.8us	552.9us	1.1us	767ns	6.7us	15.3us	173.9us
Python 3	28.1us	12.0us	8.5us	28.0us	63.3us	717.2us	2.1us	2.7us	11.0us	20.9us	12.2us
PyPy 3	1.2us	2.0us	445ns	20.5us	4.3us	107.1us	605ns	286ns	470ns	24.7us	2.0us

10000 iterations, Darwin arm64, 2026-03-14

Community

• ilo-lang.ai - docs, playground, and examples
• r/ilolang - discussion and updates
• hello@ilo-lang.ai - get in touch

Principles

1. Token-conservative - every choice evaluated against total token cost
2. Constrained - small vocabulary, one way to do things, fewer wrong choices
3. Verified - types checked before execution, all errors reported at once
4. Language-agnostic - structural tokens (@, >, ?, ^, ~, !, $) over English words

See the manifesto for full rationale.