spec

A requirements-writing and review workflow that creates a detailed specification before coding begins. EARS statements are a structured way to write testable requirements.

In plain words
What is it for?
Use it for specification-driven work, changes crossing several subsystems, or tasks that need stable requirement IDs and a mapped task list.
Why use it?
It reduces the risk of implementing an outdated, vague, or incomplete request by checking its source and mapping every requirement to planned work.

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

Made for: Claude Code, Codex.

Per session 68 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 709 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 $0.00068 $0.00709
Opus 5 $0.00034 $0.00354
Sonnet 5 $0.00014 $0.00142
Haiku 4.5 $0.00007 $0.00071

Measured yesterday against content hash eef807d2470d, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

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 yesterday.

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/spec/SKILL.md · 71 lines

How it starts

The opening of the file, as written. The whole thing — 71 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Spec

The spec path is opt-in. It turns on when the item has sdd: true, carries a decision_required field, or the change crosses several subsystems. Otherwise the item's acceptance array is the contract and you should be implementing.

Four artifacts in .mstack/specs/<slug>/, all four required before the item leaves specifying. Templates in references/templates.md, statement kit in references/ears.md.

1. Ground the spec in its source

Read what the item cites, and re-verify every file:line it references. Issues rot: one written weeks ago names code that has moved, and it can be wrong about the mechanism on the day you pick it up.

Open with the provenance:

> Source: issue #370. This spec is authoritative for implementation;
> #370 remains the discussion venue.

If the source and the spec disagree, the source is the newer intent. Stop and reconcile. Implementing an outdated spec correctly is still the wrong outcome.

2. Interview the repository, not the user

Most open questions are answered by the code, the history, or an existing decision. Go there first. Bring the human only the forks the repository genuinely cannot settle: product choices with different user-visible outcomes. Those go in decision_required, which is what triggers the human gate.

3. Requirements

Stable ids R1, R2, and EARS statements. One requirement carries one obligation.

A spec is a behaviour contract, not an implementation plan. Quick test: if the implementation could change without changing externally visible behaviour, it does not belong here.

Every acceptance bullet maps to at least one requirement. Every requirement gets at least one WHEN/THEN scenario.

4. Tasks

Every task names the requirements it covers: - [ ] 1.1 ... (covers R1, R3). The last group is always verification and close. A requirement no task covers is a requirement nobody will build.

5. Grill it, with a different pass

mstack:spec-reviewer, which has no Write and no Edit, and which must not be the pass that wrote the spec. Three questions in writing:

Read the full file on GitHub · 71 lines

Files

What ships with it

2 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 · 71 lines · 68 tokens per session scan A eef807d2470d

Subscribe to this mod's changes

spec is a skill published in the GitHub repository romerma/mstack (1 stars, last pushed 8d ago), licensed MIT. It adds 68 tokens to every session and 709 once invoked, about $0.0003 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.

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