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Agent skill

Planner Spec Expand

by Archive228 in Archive228/loopkit

Expand a 1-4 sentence product brief into a full spec with a design language, acceptance surface, and an ordered feature list.

MITAuto-check passed

Install Planner Spec Expand

skills CLI
$ npx skills add Archive228/loopkit --skill planner-spec-expand -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install Archive228/loopkit planner-spec-expand --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/Archive228/loopkit.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/planner-spec-expand .claude/skills/planner-spec-expand && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
planner-spec-expand
GitHub stars
755
Token cost
~1k tokens
SKILL.md length
537 words
Files
1
Skills in repo
43
Repo updated
First seen
Licence
MIT

At a glance

Expand a 1-4 sentence product brief into a full spec with a design language, acceptance surface, and an ordered feature list.

  • Works in 6 steps: Restate the brief in one paragraph. In… → Pick a design language. One sentence… → Enumerate the acceptance surface. For… → …
  • SKILL.md covers When to apply, Procedure — expand in this order, Checklist before you hand off and Anti-patterns, plus 1 more section
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Planner Spec Expand is an agent skill from Archive228/loopkit. Expand a 1-4 sentence product brief into a full spec with a design language, acceptance surface, and an ordered feature list.

Its SKILL.md is about 1k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

The repository describes itself as: 33 battle-tested skills + minimal .claude harness for any coding agent (Claude Code, Cursor, Codex, Gemini CLI). The licence is MIT.

Example prompts

  • “/planner-spec-expand”

Workflow steps

6 steps, taken from the first numbered list in SKILL.md.

  1. Restate the brief in one paragraph. In your own words, what is being built and for whom. If you can't write this cleanly, ask the user…
  2. Pick a design language. One sentence each on: visual tone (minimal / dense / playful), typography stance (one sans / serif+sans / mono…
  3. Enumerate the acceptance surface. For each user-observable capability, write one sentence of user-observable behavior AND the concrete…
  4. Order the features. Sort by dependency: nothing appears before what it depends on. Ties broken by "what does the user see first when they…
  5. Name the out-of-scope. One short list of things the brief could imply but you are explicitly not building. Prevents the generator from…
  6. Write the smoke path. The single user journey that proves the product exists — 3-6 steps end-to-end. This becomes the initializer's smoke…

What it can do on your machine

Read from SKILL.md and the folder at commit 5ae033e. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md.

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    Links to these hosts (documentation or services it may open):

    • prithvirajrk.com

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Planner Spec Expand loads about 1k tokens when it runs. Until then it costs about 36 tokens; SKILL.md has 537 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~36
When it runs · the whole SKILL.md, loaded when a task matches
~1k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from Archive228/loopkit at commit 5ae033e, republished under its MIT licence (© Archive228). 537 words, ~1,007 tokens.

Download SKILL.mdSave it as .claude/skills/planner-spec-expand/SKILL.md (or your agent's skills folder).
name
planner-spec-expand
description
Expand a 1-4 sentence product brief into a full spec with a design language, acceptance surface, and an ordered feature list.
when_to_use
Bootstrapping a project from a one-liner prompt before any generator agent runs, re-planning after scope creep changes the target, producing the input…

Planner Spec Expand

A one-line brief ("build a claude.ai clone", "a habit tracker with streaks") is not enough surface for a coding agent to make good decisions from. It has no design language, no acceptance criteria, no ordering. The generator ends up inventing scope mid-session and shipping incoherent slices.

The planner's job is to expand the brief into a spec dense enough that every downstream decision — what feature to pick, what "done" looks like, what the button should say — has an answer already written down. See Prithvi's post on planner/generator/evaluator separation for the underlying architecture: https://www.prithvirajrk.com/blog/three-agent-harness.

When to apply

  • The user handed you a brief under ~200 words and expects a real product.
  • You're about to seed [[feature-list-json]] and the brief has no orderable features yet.
  • Scope drifted mid-project and the original spec no longer describes the target — rewrite, don't patch.

Procedure — expand in this order

Do the sections in order. Later sections depend on earlier ones being locked.

  1. Restate the brief in one paragraph. In your own words, what is being built and for whom. If you can't write this cleanly, ask the user before continuing — the brief is under-specified.
  2. Pick a design language. One sentence each on: visual tone (minimal / dense / playful), typography stance (one sans / serif+sans / mono accents), color posture (monochrome + one accent / two-color / full palette), density (airy / compact). This locks a thousand later micro-decisions.
  3. Enumerate the acceptance surface. For each user-observable capability, write one sentence of user-observable behavior AND the concrete steps a human would take to verify it. This is the shape [[feature-list-json]] wants — write it in that shape now.
  4. Order the features. Sort by dependency: nothing appears before what it depends on. Ties broken by "what does the user see first when they open the app." The top of the list must be runnable-alone.
  5. Name the out-of-scope. One short list of things the brief could imply but you are explicitly not building. Prevents the generator from wandering.
  6. Write the smoke path. The single user journey that proves the product exists — 3-6 steps end-to-end. This becomes the initializer's smoke test.
Show full SKILL.md (186 more words)Show less

Checklist before you hand off

  • Every feature has description + steps in the shape [[feature-list-json]] expects.
  • The first 3 features can be built in order with no forward dependency.
  • Design language fits on one screen — if it's a page, you over-specified.
  • Out-of-scope list is non-empty. If everything is in scope, you didn't plan, you transcribed.
  • Smoke path touches the core value prop, not auth or settings.

Anti-patterns

  • Padding the feature list to look thorough. 40 real features beats 200 fake ones. The generator will build all of them.
  • Designing the schema. That's the generator's job. You describe user-observable behavior; the generator picks the data model.
  • Writing prose where you should write steps. "User can manage conversations" is not a feature. "Clicking the trash icon on a sidebar item deletes that conversation and removes it from the sidebar" is.
  • Leaving priority implicit. If two features tie, break the tie now. The generator will not.

When NOT to apply

Skip this for briefs already specified to acceptance-criteria depth, or for single-feature edits to an existing project — use [[shift-notes]] and pick from the existing [[feature-list-json]] instead.

Related: [[feature-list-json]], [[shift-notes]], [[broken-window-check]].

© Archive228, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in skills/planner-spec-expand of Archive228/loopkit.

Open the folder on GitHubat commit 5ae033e

Compare with similar skills

Planner Spec Expand next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Planner Spec Expand compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Planner Spec Expand this skillArchive228/loopkit755—~1kAutomated safety check: PassMIT
Briefalirezarezvani/claude-skills28k—~967Automated safety check: PassMIT
Plannerpenpot/penpot61k—~2.7kAutomated safety check: PassMPL-2.0
Agent Plannerruvnet/ruflo74k2 repos~1.2kAutomated safety check: PassMIT
Briefdavepoon/buildwithclaude3.6k—~1.3kAutomated safety check: NotesMIT
Agent Goal Plannerruvnet/ruflo74k2 repos~842Automated safety check: PassMIT

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Questions about Planner Spec Expand

What does Planner Spec Expand do?

Expand a 1-4 sentence product brief into a full spec with a design language, acceptance surface, and an ordered feature list. Planner Spec Expand is an agent skill from Archive228/loopkit. Expand a 1-4 sentence product brief into a full spec with a design language, acceptance surface, and an ordered feature list.

How do I install Planner Spec Expand in Claude Code?

Run `npx skills add Archive228/loopkit --skill planner-spec-expand -a claude-code`. Or copy the skill folder (skills/planner-spec-expand in Archive228/loopkit) into .claude/skills/planner-spec-expand in your project. Claude Code loads it when a task matches its description.

How do I install Planner Spec Expand in Codex?

Run `npx skills add Archive228/loopkit --skill planner-spec-expand -a codex`. Or copy the skill folder (skills/planner-spec-expand in Archive228/loopkit) into .agents/skills/planner-spec-expand in your project. Codex loads it when a task matches its description.

Can I use Planner Spec Expand in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add Archive228/loopkit --skill planner-spec-expand -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/planner-spec-expand, .gemini/skills/planner-spec-expand, .github/skills/planner-spec-expand and .opencode/skills/planner-spec-expand in your project.

What does Planner Spec Expand need to run?

SKILL.md names no scripts, command-line tools or credentials: Planner Spec Expand is instructions for the agent only.

Does Planner Spec Expand access the network?

SKILL.md names 1 domain. As links in the text: prithvirajrk.com. This is read from the text; nothing was executed.

Is Planner Spec Expand safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Planner Spec Expand use?

Planner Spec Expand is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Planner Spec Expand use?

About 1k tokens (SKILL.md is roughly 4k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Planner Spec Expand?

Skills that share tags, products or a category with Planner Spec Expand: Brief (alirezarezvani/claude-skills, 28k stars), Planner (penpot/penpot, 61k stars), Agent Planner (ruvnet/ruflo, 74k stars) and Brief (davepoon/buildwithclaude, 3.6k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Planner Spec Expand?

Archive228 (a GitHub user) maintains it in Archive228/loopkit, which has 755 GitHub stars. The repository holds 43 skills in this directory. The repository was last updated on July 14, 2026.

Source: Archive228/loopkit on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.