Record just --version and read the existing justfile, imports, modules, and settings. Use only features the project's minimum version supports; the cards give the version for each attribute and setting.
Find the canonical command for each operation (package scripts, cargo, uv run, a script under scripts/); the recipe calls it, it does not re-implement it (wrapping).
Decide how arguments reach the command (arguments). Anything user-supplied goes through [positional-arguments] with "$@", an exported (dollar-prefixed) parameter, or quote(); never bare {{ arg }}.
Add dependencies, attributes ([group], [private], [confirm], platform attributes), and settings only where the cards' Use when applies.
Run just --fmt then just --fmt --check, just --list, and just --dry-run RECIPE.
Run each new recipe for real: normal arguments, an argument with a space and a $, a failing underlying command (check just's exit status), and the confirm path for destructive recipes.
Report the commands run and their output.

Route the task to a card

Task or symptom	Card
New recipe for an existing command	Wrapping
Arguments with spaces split or break	Interpolation splits, quote(), positional, exported
Optional parameter	Defaults
Forward a list of files or test filters	Variadic
`--flag value` style options, value validation	arg attribute
Step A must run before B	Prior dependencies
Step must run only after success	Subsequent dependencies
Same recipe for several targets	Dependency arguments
Independent slow steps	Parallel
`cd` or variables lost between lines	Line shells, Script recipes
Recipe reports success after a failure	Failure stops, ignore-error prefix
Deletes, deploys, publishes	Confirm
Different commands per OS	Platform attributes
Recipe runs in the wrong directory	Working directory
`just --list` is unclear	Default, private, groups, docs
Subproject recipes	Modules
Shared values, paths	Variables, env(), overrides
Value depends on CI or OS	Conditionals
Every recipe is slow or fails on a missing tool	Backticks and lazy, require()
Tool reads environment variables	Exporting, Dotenv
Pipelines hide failures, Windows shell	Shell setting
Contributors on old just	minimum-version
Proving the justfile works	Verification

Rules

A recipe calls the project's canonical command; it does not duplicate build logic, and it does not replace a working build system.
User-supplied values never reach a shell through bare {{ arg }}.
A recipe's exit status is the wrapped command's: no - prefix, || true, or unchecked pipeline to make a failing check pass.
Destructive recipes carry [confirm]; CI passes --yes explicitly.
Use features only if the project's just version has them; state the minimum (set minimum-version, 1.55.0+) when adding newer attributes.
Do not use the deprecated env_var, env_var_or_default, set windows-shell, or set windows-powershell in new code.
just --fmt --check and --dry-run prove syntax and command text, not behavior; run the recipe.

Bundled tools

assets/examples/verify.sh: runs every example recipe in a temporary copy and compares output and exit status; prints SKIP if just is missing.
scripts/check_justfiles.py PATH...: runs just --fmt --check on every justfile under the paths; exit 0 pass, 1 format failure, 2 bad input.

References

Arguments: interpolation, quote(), positional and exported arguments, defaults, variadics, [arg].
Recipes: wrapping, dependencies (prior, subsequent, with arguments, parallel), line versus script recipes, failure handling, confirm, platforms, working directory, listing, modules.
Variables and settings: strings, env(), overrides, conditionals, backticks and set lazy, exports, dotenv, shell, require(), minimum-version.
Verification: --fmt --check, listing, --dry-run, --evaluate, JSON dump, argument probes, exit status, batch checks.

Completion evidence

The report includes just --version, the just --fmt --check result, the just --list output for new recipes, each new recipe's real run with an argument containing a space (output shown), a failing-command run with its exit status, and anything not run (for example a Windows-only recipe), stated as not verified.

write-justfiles

Write Justfiles

Workflow