specification-capture

specification-capture is a skill for Claude Code from synaptiai/synapti-marketplace. It costs 121 tokens per session (2,652 once invoked), scanned A, original, Apache-2.0.

A method for recording an issue's non-goals, failure cases, and interface contracts in a decision journal. An interface contract describes how a component is expected to be used.

In plain words
What is it for?
Use it when starting an issue, design discussion, or brainstorming session to capture what is out of scope, what can go wrong, and how interfaces must behave.
Why use it?
It prevents unclear scope and missing failure behavior from being carried into design and implementation.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter. Also seen: agent in frontmatter; names the AskUserQuestion tool; positional $N argument.

Part of the flow plugin — 31 skills, 21 commands, 9 agents shipped together

Good fit Use it when starting an issue, design discussion, or brainstorming session to capture what is out of scope, what can go wrong, and how interfaces must behave.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/synaptiai/synapti-marketplace/specification-capture
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.

Any agent
npx skills add synaptiai/synapti-marketplace --skill specification-capture
Clone the repo
git clone --depth 1 https://github.com/synaptiai/synapti-marketplace

Made for: Claude Code.

Or install flow, the plugin that ships this one along with the rest of its 31 skills, 21 commands, 9 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 specification-capture

README.md
[![agentmods](https://agentmods.dev/badge/skills/synaptiai/synapti-marketplace/specification-capture/github.svg)](https://agentmods.dev/skills/synaptiai/synapti-marketplace/specification-capture)
Your own site
<a href="https://agentmods.dev/skills/synaptiai/synapti-marketplace/specification-capture"><img src="https://agentmods.dev/badge/skills/synaptiai/synapti-marketplace/specification-capture/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for specification-capture

Your own site · 80×15
<a href="https://agentmods.dev/skills/synaptiai/synapti-marketplace/specification-capture"><img src="https://agentmods.dev/badge/skills/synaptiai/synapti-marketplace/specification-capture.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 121 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,652 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00121 $0.02652
Opus 5 $0.00060 $0.01326
Sonnet 5 $0.00024 $0.00530
Haiku 4.5 $0.00012 $0.00265

Measured 6d ago against content hash 04471f1a396e, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

specification-capture 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 6d 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.

plugins/flow/skills/specification-capture/SKILL.md · 162 lines

How it starts

The opening of the file, as written. The whole thing — 162 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Specification Capture

You capture three specification elements that complement an issue's acceptance criteria, and you persist them to the decision journal so every downstream phase (PLAN, CODE, VERIFY) and every related command (/flow:design, /flow:brainstorm) can read from the same source of truth.

This skill owns the capture lifecycle and the journal contract — every consumer (/flow:start, /flow:design, /flow:brainstorm) invokes the skill instead of re-implementing it. Two failure modes the skill prevents:

  1. No persistence-side check — without a single owner, a command can claim "captured all three" while writing only a partial set to the journal, and the gap silently flows into PLAN.
  2. No shared source of truthcommands/design.md and commands/brainstorm.md would otherwise address overlapping elements (non-goals especially) without reading from or writing to the same .decisions/ artifact, so a user running /flow:design first and /flow:start second would get duplicate or contradictory specifications.

Iron Law

EVERY ISSUE GETS THE THREE ELEMENTS BEFORE PLAN. Acceptance criteria scope WHAT the user-visible outcome is. The three elements scope what the implementation IS NOT, how it behaves under failure, and what schemas it must honor. PLAN cannot fence the implementation without all three.

A captured specification is the contract between the issue and the per-task atomic units the implementation-planner agent produces. Without it, tasks lack failure-mode coverage and interface contracts — the Stranger Test (end-of-PLAN gate in commands/start.md) will fail.

Inputs

The invoking command MUST pass these in the prompt:

  1. Issue context — title, body, labels, comments. The skill parses these for any specification language already in the issue.
  2. Journal path — typically .decisions/issue-{N}.md (where {N} is the issue number). The skill reads this path first to detect prior captures.
  3. Invocation reason — one of start, design, brainstorm. Used to scope which elements the skill focuses on (see "Per-invoker scope" below).

Read the full file on GitHub · 162 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. 6d ago First seen · 162 lines · 121 tokens per session scan A 04471f1a396e

Subscribe to this mod's changes

specification-capture is a skill published in the GitHub repository synaptiai/synapti-marketplace (6 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 121 tokens to every session and 2,652 once invoked, about $0.0006 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 2026-09-03.