How do I install the Justfile Dev skill?

Run npx skillmds@latest add arustydev/justfile-dev in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

What does the Justfile Dev skill do?

Justfile authoring, reviewing, and planning for the just command runner. Use when creating new justfiles, adding recipes, reviewing existing justfiles for quality, planning recipe sets for new projects, or upgrading justfiles as projects mature. Covers syntax patterns, module system, recipe groups, language-specific templates, and maturity assessment. It is listed under Coding & Dev Tools on SkillMD.

Is Justfile Dev safe to use?

SkillMD's automated safety review verdict for this skill is PASS. Independent scanners report: SkillSpector: PASS, Skill Scanner: PASS. Capability flags: makes network calls. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Justfile Dev?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Justfile Dev free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Justfile Dev?

aRustyDev (@arustydev) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Justfile Dev by arustydev — Agent Skill

Name: Justfile Dev
Rating: 4.2 (5 reviews)
Author: aRustyDev

Justfile Development

Workflows for authoring, reviewing, planning, and updating justfiles with the just command runner.

When to Use

Creating a new justfile for a project
Adding or modifying recipes
Reviewing a justfile for quality issues
Planning which recipes a project needs
Upgrading a justfile as a project matures
Converting a Makefile to a justfile
Setting up monorepo module structure

Workflows

Author

When creating a new justfile or adding recipes.

New Justfile Scaffold:

set shell := ["bash", "-cu"]

default:
    @just --list

# =============================================================================
# Development
# =============================================================================

# Build the project
[group('dev')]
build:
    <build-command>

# =============================================================================
# Testing
# =============================================================================

# Run test suite
[group('test')]
test:
    <test-command>

# =============================================================================
# Code Quality
# =============================================================================

# Format code
[group('lint')]
fmt:
    <fmt-command>

# Run linter
[group('lint')]
lint:
    <lint-command>

# =============================================================================
# Utilities
# =============================================================================

# Remove build artifacts
[group('util')]
[confirm('Remove all build artifacts?')]
clean:
    <clean-command>

Recipe Writing Rules:

Rule	Example
Always add `[group('name')]`	`[group('dev')]`
Doc comment above every recipe	`# Build the project`
Private helpers start with `_`	`_ensure-tool name:`
`[confirm]` on destructive ops	`[confirm('Delete all?')]`
Prefer parameters over env vars	`recipe name='default':`
Single responsibility	Compose with dependencies
No `&&` chaining	Use separate lines or deps
No `cd`	Use `[working-directory]`

Adding Recipes to Existing Justfiles:

Identify the correct group (see Standard Groups below)
Place recipe near related recipes in the same section
Add doc comment
Add [group] attribute
If destructive, add [confirm]

Review

Use this checklist when reviewing justfiles.

## Justfile Review

- [ ] `set shell` declared at top
- [ ] All recipes grouped with `[group('name')]`
- [ ] Every recipe has a doc comment
- [ ] No ungrouped recipes (except `default`)
- [ ] Private helpers prefixed with `_`
- [ ] Destructive recipes use `[confirm]`
- [ ] No `cd` usage (use `[working-directory]`)
- [ ] No `&&` chaining (use dependencies or separate lines)
- [ ] No secrets in justfile (env vars or `op://`)
- [ ] `default` recipe shows `just --list`
- [ ] Section separators between groups
- [ ] Recipe names are kebab-case
- [ ] No monolithic recipes (compose from focused ones)
- [ ] Parameters preferred over env vars for inputs

Common Issues:

Issue	Fix
Missing `set shell`	Add `set shell := ["bash", "-cu"]` at top
Ungrouped recipes	Add `[group('name')]` attribute
Missing doc comments	Add `# Description` above recipe
`cd` in recipe body	Use `[working-directory('path')]`
`&&` chaining	Split into separate lines or deps
Hardcoded secrets	Replace with `env('VAR')` or `op://`
God recipe doing everything	Split into focused recipes, compose with deps

Plan

Use when deciding what recipes a project needs.

3-Question Assessment:

Question	Yes	No
Has CI?	Add quality gates (coverage, check-all)	Skip quality recipes
Deploys to prod?	Add security + deploy recipes	Skip deploy/security
Multiple languages?	Add module structure	Keep single justfile

Recipe Sets by Project Type:

Project Type	Baseline	Quality	Deploy	Modules
Rust CLI	build, test, lint, fmt, clean	coverage, bench, release	docker	—
Rust lib	build, test, lint, fmt, docs	coverage, bench	release	—
Web app	build, test, lint, fmt, dev	coverage	docker, deploy	if polyglot
Monorepo	orchestrate, default	per-package	per-service	yes
MCP server	build, test, lint, fmt	coverage	docker, release	—

Decision: Single File vs Modules:

Criteria	Single `justfile`	Modules
Recipe count	< 20	> 20
Languages	1	2+
Repo structure	flat	monorepo/workspace
Shared recipes	none	CDN imports needed

Convert

When migrating from a Makefile to a justfile.

Steps:

Map targets to recipes (all recipes are phony — no .PHONY needed)
Add set shell := ["bash", "-cu"] at top
Add default recipe with @just --list
Group recipes with [group('name')] and add section separators
Add doc comments above each recipe
Fix anti-patterns (see translations below)
Add [confirm] to destructive recipes
Validate: just --list shows grouped, documented recipes

Makefile → just Translations:

Makefile	just
`.PHONY: target`	Not needed (all recipes are phony)
`target: dep1 dep2`	`recipe: dep1 dep2` (same syntax)
`cd dir && cmd`	`[working-directory('dir')]` attribute
`cmd1 && cmd2`	Separate lines in recipe body
`$(VAR)`	`{{VAR}}`
`@echo "msg"`	`@echo "msg"` (same)
`export VAR=val`	`export VAR := "val"` at top
`include file.mk`	`import "file.just"`

Update

When upgrading an existing justfile.

Maturity Progression:

Level	When	Add
0: Baseline	Every project	default, build, test, lint, fmt, clean
1: Quality	CI/CD added	coverage, test-watch, check-all, bench
2: Security	Deploying	audit, sbom, doctor
3: Production	Prod systems	deploy, migrate, logs, status
4: Polyglot	Multi-language	modules, orchestration

YAGNI: Only add levels you currently need. Reassess when project scope changes.

Module Migration:

When a justfile exceeds ~20 recipes, consider splitting:

Create just/ directory
Move related recipes to just/<group>.just
Add import? "just/<group>.just" to root justfile
Or use CDN: mod name "https://just.arusty.dev/modules/<name>.just"

Quick Reference

Standard Groups

Group	Purpose	Typical Recipes
`dev`	Development	build, setup, install, watch, dev
`test`	Testing	test, coverage, bench, test-watch
`lint`	Code quality	fmt, lint, clippy, check
`docs`	Documentation	docs-build, docs-serve
`docker`	Containers	docker-build, docker-run, docker-push
`release`	Publishing	release, version-bump, changelog
`util`	Maintenance	clean, update, doctor

Essential Syntax

Feature	Syntax
Settings	`set shell := ["bash", "-cu"]`
Groups	`[group('dev')]`
Confirm	`[confirm('message')]`
Working dir	`[working-directory('path')]`
Private	`_recipe-name:`
Parameters	`recipe name:`
Default params	`recipe name='value':`
Variadic	`recipe *args:`
Dependencies	`recipe: dep1 dep2`
Param deps	`recipe: (dep1 "arg")`
Conditional	`if os() == "macos" { ... }`
Shebang	`#!/usr/bin/env python3`
Script attr	`[script('python3')]`
Optional import	`import? "just/mod.just"`
CDN module	`mod name "https://url"`

Common Functions

Function	Returns
`os()`	`"linux"`, `"macos"`, `"windows"`
`arch()`	`"x86_64"`, `"aarch64"`
`env('VAR')`	Environment variable value
`env('VAR', 'default')`	With fallback
`justfile_directory()`	Dir containing justfile
`invocation_directory()`	Dir where `just` was called

aRustyDev Conventions

Shell: always set shell := ["bash", "-cu"]
CDN modules from just.arusty.dev
Local modules in just/ with import?
Gist templates via just apply-gist (see gist-templates rule)
KuzuDB recipes follow graph-data-pattern rule

Language Patterns

Quick lookup — see references/recipe-patterns.md for full details.

Recipe	Rust	Go	TypeScript	Python
`fmt`	`cargo fmt`	`gofmt -w .`	`prettier --write .`	`ruff format .`
`lint`	`cargo clippy`	`golangci-lint run`	`eslint .`	`ruff check .`
`test`	`cargo test`	`go test ./...`	`vitest`	`pytest`
`build`	`cargo build`	`go build ./...`	`tsc`	`python -m build`
`coverage`	`cargo tarpaulin`	`go test -cover`	`vitest --coverage`	`pytest --cov`

Justfile Dev

File contents

Justfile Development

When to Use

Workflows

Author

Review

Plan

Convert

Update

Quick Reference

Standard Groups

Essential Syntax

Common Functions

aRustyDev Conventions

Language Patterns

See Also

Frequently asked questions

Justfile Dev

File contents

Justfile Development

When to Use

Workflows

Author

Review

Plan

Convert

Update

Quick Reference

Standard Groups

Essential Syntax

Common Functions

aRustyDev Conventions

Language Patterns

See Also

Related skills

Frequently asked questions

How do I install the Justfile Dev skill?

What does the Justfile Dev skill do?

Is Justfile Dev safe to use?

Which AI agents work with Justfile Dev?

Is Justfile Dev free to use?

Who published Justfile Dev?