write-product-spec

A workflow for writing a product specification: a shared description of what a significant or unclear feature should do. It focuses on observable behavior so implementers and reviewers can agree on the result.

In plain words
What is it for?
Use it to document feature behavior, user impact, edge cases, validation needs, and relevant issue context in a repository specification file.
Why use it?
It reduces ambiguity before coding starts, including uncertainty about scope, affected users, edge cases, and validation. It is intended for substantial work rather than small fixes or simple refactors.

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/terry-mao/aicodingflow/write-product-spec
Any agent
npx skills add Terry-Mao/AICodingFlow --skill write-product-spec
Clone the repo
git clone --depth 1 https://github.com/Terry-Mao/AICodingFlow

Made for: Claude Code, Codex.

Per session 20 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 690 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 $0.00020 $0.00690
Opus 5 $0.00010 $0.00345
Sonnet 5 $0.00004 $0.00138
Haiku 4.5 $0.00002 $0.00069

Measured 3d ago against content hash 1db722c2befc, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

write-product-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 3d 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.

.agents/skills/write-product-spec/SKILL.md · 69 lines

How it starts

The opening of the file, as written. The whole thing — 69 lines — stays where its author put it; the contents beside it link to each section on GitHub.

write-product-spec

Write the product contract an implementer and reviewer can use to agree on observable behavior. This is a local shared skill; wrappers may provide exact inputs and output paths that take precedence.

Decide and prepare

Use it when behavior, scope, risk, or user impact is substantial enough that a checked-in spec will reduce ambiguity. Skip it for small fixes, straightforward refactors, and narrow low-risk changes.

Specs normally live under specs/. Without an explicit wrapper or prompt path, use specs/<topic>/product.md; preserve this repository's lowercase filenames and issue-backed layout. Do not create an issue or other tracker item unless the user explicitly asks.

Gather only the feature summary, affected users/consumers, desired behavior, edge cases, validation needs, and relevant issue context. Here, “user” may be an end user, maintainer, operator, API caller, contributor, or agent consuming the designed surface. Ask about missing product decisions instead of guessing.

For UI or interaction work, ask whether a Figma mock exists before drafting behavior. Include its link, or explicitly write Figma: none provided; skip this for non-visual features.

Write the spec

Keep the spec implementation-light. Required sections are:

  1. Summary — the feature and desired outcome in 1–3 sentences.
  2. Problem — the user or product problem when it is not already obvious.
  3. Goals — observable outcomes the change must achieve.
  4. Non-goals — adjacent work that is intentionally out of scope.
  5. Figma / design references — only for visual work; include the link or explicit absence.
  6. User experience — the main contract. Prefer numbered, testable behavior invariants covering defaults, inputs, state transitions, loading/empty/error states, cancellation, stale or missing data, permissions, races, and keyboard/accessibility expectations when relevant.
  7. Success criteria — concrete outcomes a reviewer can observe; do not duplicate the behavior section with generic quality claims.
  8. Validation — how the behavior will be checked with tests or manual evidence. Keep implementation-specific test design in the tech spec too.
  9. Open questions — unresolved product decisions, preferably next to the behavior they affect.

Read the full file on GitHub · 69 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. 3d ago First seen · 69 lines · 20 tokens per session scan A 1db722c2befc

Subscribe to this mod's changes

write-product-spec is a skill published in the GitHub repository Terry-Mao/AICodingFlow (165 stars, last pushed 5d ago), licensed MIT. It adds 20 tokens to every session and 690 once invoked, about $0.0001 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.

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