makrell-data

name	makrell-data
description	Work with Makrell data and markup formats — MRON (.mron), MRML (.mrml), and MRTD (.mrtd). Use when creating, editing, validating, or explaining these formats.
allowed-tools	Read Grep Glob Edit Write Bash

Makrell Data Formats

You are helping in a project that uses Makrell data and markup formats. These formats share the MBF structural core with the Makrell language family.

Format Overview

Format	Purpose	File ext	Closest analogue
MRON	Data notation (config, API)	.mron	JSON / TOML
MRML	Markup notation	.mrml	HTML / XML
MRTD	Tabular data	.mrtd	CSV / TSV

---

MRON — Makrell Object Notation

MRON is a Makrell-shaped alternative to JSON. Lighter punctuation, same structural expressiveness.

Scalars

name "Rena Holm"
count 42
pi 3.14
active true
missing null

Strings require double quotes. Numbers, booleans (true/false), and null are bare.

Objects (top-level)

project "Makrell"
version "0.10.0"
active true

A top-level MRON document is implicitly an object — each line is a key/value pair.

Lists

tags ["docs" "formats" "languages"]
scores [95 87 91]

Square brackets, space-separated values.

Nested objects

site {
    title "makrell.dev"
    sections [
        {
            name "concepts"
            public true
        }
        {
            name "tutorials"
            public true
        }
    ]
}

Curly braces for nested objects. Lists of objects use [{ ... } { ... }].

Complete example

owner "Rena Holm"
last_update "2026-04-03"

books [
    {
        title "That Time of the Year Again"
        year 1963
        author "Norton Max"
    }
    {
        title "One for the Team"
        year 2024
        author "Felicia X"
    }
]

MRON vs JSON mapping

JSON	MRON
{ "key": "value" }	key "value"
{ "a": [1, 2, 3] }	a [1 2 3]
{ "x": { "y": 1 } }	x { y 1 }
"string"	"string"
42, true, null	42, true, null
commas, colons	whitespace separation

---

MRML — Makrell Markup Language

MRML is a Makrell-shaped alternative to HTML/XML. Tree structure expressed through nested curly forms.

Basic elements

{h1 Hello World}
{p This is a paragraph.}

The first token after { is the tag name. Everything else is content.

Attributes

{p [class="lead" id="intro"]
    A paragraph with attributes.}

Square brackets after the tag name hold attributes.

Nested structure

{html
    {head
        {title A Test}}
    {body
        {h1 This is a Test}
        {p [style="color: red"] Just some {b bold} text here.}}}

Inline elements

{p Use the {b shared concepts} section first.}
{p Visit {a [href="/docs"] the docs} for more.}

Complete page example

{html
    {head
        {meta [charset="utf-8"]}
        {title My Page}
        {link [rel="stylesheet" href="style.css"]}}
    {body
        {header
            {nav
                {a [href="/"] Home}
                {a [href="/about"] About}}}
        {main
            {section [class="hero"]
                {h1 Welcome}
                {p One structural family for code, data, and markup.}}
            {section [class="features"]
                {div [class="card"]
                    {h2 Functional}
                    {p Pipes, operators, and composition.}}
                {div [class="card"]
                    {h2 Multi-host}
                    {p Python, TypeScript, and .NET.}}}}
        {footer
            {p Built with Makrell.}}}}

MRML vs HTML mapping

HTML	MRML
<h1>Title</h1>	{h1 Title}
<p class="x">Text</p>	{p [class="x"] Text}
<div><p>A</p><p>B</p></div>	{div {p A} {p B}}
<a href="/">Home</a>	{a [href="/"] Home}
Close tags	Closing } (structural nesting)

---

MRTD — Makrell Tabular Data

MRTD is a whitespace-separated tabular format. Simpler than CSV for many common shapes.

Untyped (header + data)

name city
Ada Oslo
Ben Bergen

The first row is the header. Subsequent rows are data. Cells are whitespace-separated.

Typed columns

name:string age:int active:bool
Ada 32 true
"Rena Holm" 29 false

Header cells can carry type annotations: int, float, bool, string.

Quoted values

"full name":string city:string
"Rena Holm" "Bergen sentrum"

Quote values that contain spaces or are not valid identifiers.

Multiline rows

name:string note:string score:float
( "Rena Holm"
  "line wrapped"
  13.5 )

Wrap rows in ( ) when they need to span multiple lines.

Profiles (extended scalars)

when bonus
"2026-04-03"dt 3k

The extended-scalars profile adds suffixed literals like date (dt) and numeric shortcuts (k, M). Profiles are opt-in.

MRTD vs CSV mapping

CSV	MRTD (untyped)	MRTD (typed)
name,age,active	name age active	name:string age:int active:bool
Ada,32,true	Ada 32 true	Ada 32 true
"Rena Holm",29,false	"Rena Holm" 29 false	"Rena Holm" 29 false
Comma-separated	Whitespace-separated	Whitespace-separated
No type info	No type info	Type annotations in header

---

Validation commands

All three formats can be checked via CLI:

makrellsharp check-mron file.mron --json
makrellsharp check-mrml file.mrml --json
makrellsharp check-mrtd file.mrtd --json

Programmatic access

Python (MakrellPy)

from makrell.mrtd import read_records
rows = read_records("""
name:string age:int active:bool
Ada 32 true
Ben 41 false
""")

TypeScript (MakrellTS)

import { parseMrtd, readMrtdRecords } from "makrellts";
const rows = readMrtdRecords(`
name:string age:int active:bool
Ada 32 true
Ben 41 false
`);

C# (Makrell#)

var rows = MrtdTyped.ReadRecords<Person>("""
    name:string age:int active:bool
    Ada 32 true
    Ben 41 false
    """);

Guidelines

When writing MRON:

• No commas or colons between keys and values — use whitespace
• Strings always use double quotes
• Top-level is implicitly an object

When writing MRML:

• First token after { is the element name
• Attributes go in [...] immediately after the tag name
• Close with }, not a closing tag — nesting is structural

When writing MRTD:

• First row is always the header
• Whitespace separates cells, not commas
• Quote any value containing spaces
• Type annotations are optional: name and name:string are both valid headers

Documentation

• MRON: https://makrell.dev/mron/
• MRML: https://makrell.dev/mrml/
• MRTD: https://makrell.dev/mrtd/
• MBF (shared structure): https://makrell.dev/mbf/