shape-spec

shape-spec is a skill for Claude Code, Codex from duthaho/claudekit. It costs 102 tokens per session (2,758 once invoked), scanned A, original, MIT.

A short requirements-writing workflow for a non-trivial feature, change, or refactor. It produces a written specification describing the goal, boundaries, constraints, acceptance checks, and unresolved questions.

In plain words
What is it for?
Use it when defining what a feature should do, aligning stakeholders, coordinating work across modules or services, or documenting acceptance criteria.
Why use it?
It turns an unclear request into an agreed description before anyone makes a plan or writes code.

Skill for Claude CodeCodex

Part of the claudekit plugin — 15 skills, 8 agents shipped together

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/duthaho/claudekit/shape-spec
Any agent
npx skills add duthaho/claudekit --skill shape-spec
Clone the repo
git clone --depth 1 https://github.com/duthaho/claudekit

Made for: Claude Code, Codex.

Or install claudekit, the plugin that ships this one along with the rest of its 15 skills, 8 agents.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for shape-spec

README.md
[![agentmods](https://agentmods.dev/badge/skills/duthaho/claudekit/shape-spec.svg)](https://agentmods.dev/skills/duthaho/claudekit/shape-spec)
Your own site
<a href="https://agentmods.dev/skills/duthaho/claudekit/shape-spec"><img src="https://agentmods.dev/badge/skills/duthaho/claudekit/shape-spec.svg" alt="Measured on agentmods" height="20"></a>
Per session 102 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,758 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 $0.00102 $0.02758
Opus 5 $0.00051 $0.01379
Sonnet 5 $0.00020 $0.00552
Haiku 4.5 $0.00010 $0.00276

Measured 5d ago against content hash e8117f3b4912, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

shape-spec 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 5d ago.

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-spec/SKILL.md · 198 lines

How it starts

The opening of the file, as written. The whole thing — 198 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Shape Spec

Overview

A short structured workflow that turns a vague request ("we need to add X") into a written spec that can be reviewed and planned against. The skill exists because the most expensive engineering bug is the wrong feature shipped well — and the second most expensive is the right feature with a missing constraint nobody wrote down. A spec is not a plan; it does not answer "how." It answers what, why, and what's out of bounds. The deliverable is a one-to-three page Markdown document a teammate can read in 5 minutes and sign off on, or push back against. Used before any plan is written.

When to Use

  • A feature has been discussed informally and someone needs to write it down
  • Multiple stakeholders disagree on scope and you need a shared text to argue against
  • The change touches more than one module or service (multi-team coordination)
  • A previous attempt at this work was abandoned or shipped wrong, and you're not sure why
  • You're about to start /claudekit:write-plan and realize you can't define acceptance criteria yet

When NOT to Use

  • The change is one-line, single-file, single-author
  • A spec already exists; you should be reviewing it, not rewriting it
  • You're in the middle of debugging — debugging produces a fix, not a spec. Use /claudekit:investigate-root-cause.

Process

Step 0: Size the change

Goal: Scale the ceremony to the change before spending it. A full spec on a one-line fix trains people to skip the whole discipline; no spec on a multi-module change is how the missing constraint ships.

Actions:

  1. Classify the change (when unsure between two tiers, pick the smaller and say so — the plan contract upgrades it later if the work grows):
    • Trivial — one-line / single-file / describable in one sentence. Stop here — no spec. Make the change, then go straight to verification-gate and code-review-loop.
    • Small — one focused change, ≤ ~3 files, design obvious. Skip the spec and plan-review; hand off to write-plan for a lightweight inline plan.
    • Standard — multi-file, multi-session, or real design decisions. Continue to Step 1 and write the full spec.
  2. Whatever the tier, the evidence never scales to zero: verification-gate runs and code-review-loop reviews any shipped diff. Ceremony is what scales, not the gate. (Full tier table: README "Sizing the work".)

Read the full file on GitHub · 198 lines

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. 5d ago First seen · 198 lines · 102 tokens per session scan A e8117f3b4912

Subscribe to this mod's changes

shape-spec is a skill published in the GitHub repository duthaho/claudekit (97 stars, last pushed 1mo ago), licensed MIT. It adds 102 tokens to every session and 2,758 once invoked, about $0.0005 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 2026-08-30.