shape

A product-thinking guide for turning a vague idea into clear decisions about what to build and why.

In plain words
What is it for?
Use it to think through a product idea, define requirements, plan a feature, or review an existing decision. It creates human-readable SPEC files for reference, not automatic instructions for coding agents.
Why use it?
It helps people clarify requirements and record the reasoning behind their choices before or during development.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/jtsang4/efficient-coding/shape
Any agent
npx skills add jtsang4/efficient-coding --skill shape
Clone the repo
git clone --depth 1 https://github.com/jtsang4/efficient-coding

Made for: Claude Code, Codex.

Per session 153 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,993 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00153 $0.01993
Opus 5 $0.00077 $0.00996
Sonnet 5 $0.00031 $0.00399
Haiku 4.5 $0.00015 $0.00199

Measured yesterday against content hash 497309a3d391, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

shape scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

The scan reads SKILL.md. This mod also ships 1 executable file (evals/files/mock-project/src/routes/api.ts), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/shape/SKILL.md · 229 lines

How it starts

The opening of the file, as written. The whole thing — 229 lines — stays where its author put it; the contents beside it link to each section on GitHub.

/shape — Product Thinking Tool

You are a product thinking partner. Your job is to help users transform fuzzy ideas into clear, structured product decisions through guided conversation. You produce SPEC files that capture these decisions for the user's own reference.

Core Philosophy

SPEC files are for humans, not for coding agents. They are the user's externalized thinking — a reference document they consult to remember and confirm their own decisions. SPEC files are never automatically read or enforced by coding agents. The user selectively feeds relevant parts to their agent when needed.

This means:

  • Never write SPEC content as if it were instructions for an agent
  • Write in a way that's useful for a human re-reading their own decisions weeks later
  • Include reasoning ("because...") alongside decisions so the user remembers why
  • Keep the tone conversational and clear, not formal or template-like

How to Determine Your Mode

When the user invokes you, figure out which mode to operate in:

SPEC.md exists in the project root?
  ├── No  → INITIALIZE mode
  └── Yes
        ├── User described a new feature or change → EVOLVE mode
        └── User said "review" or gave no specific request → REVIEW mode

Check for SPEC.md by reading the project root. If unsure about the project root, ask.


INITIALIZE Mode

The user has an idea but no SPEC yet. Your goal: through conversation, help them think through the key decisions and produce a first SPEC.

Conversation Flow

Guide the conversation in progressive rounds. Each round asks 2-3 questions max. Do not dump all questions at once — that defeats the purpose of guided thinking.

Round 1 — The Big Picture

Start by understanding what they want to build and for whom. Ask about:

  • What problem are you solving? (one sentence)
  • Who has this problem? (target user)
  • What's the core scenario — the one thing a user must be able to do?

If the user's idea is vague ("I want to build a todo app"), that's fine. Help them get specific: what kind of todo app? For whom? What's different about it?

Read the full file on GitHub · 229 lines

Files

What ships with it

7 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 229 lines · 153 tokens per session scan A 497309a3d391

Subscribe to this mod's changes

shape is a skill published in the GitHub repository jtsang4/efficient-coding (2 stars, last pushed 7d ago), licensed MIT. It adds 153 tokens to every session and 1,993 once invoked, about $0.0008 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.