What is spec-best-practices?

A guide for creating and maintaining SPEC.md files, which are Markdown documents that describe a project's problem, design, and requirements. It also covers the /specout command and an ADF specification checkpoint.

Use it when creating, reviewing, or updating SPEC.md files or entering the ADF SPEC gate.

It prevents inconsistent spec names, locations, and contents across a codebase.

How alleneubank/claude-code configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to alleneubank/claude-code. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/alleneubank/claude-code/main/.claude/skills/spec-best-practices/SKILL.md

Clone the repo

git clone --depth 1 https://github.com/alleneubank/claude-code

Made for: Claude Code.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/alleneubank/claude-code/spec-best-practices/github.svg)](https://agentmods.dev/skills/alleneubank/claude-code/spec-best-practices)

Your own site

<a href="https://agentmods.dev/skills/alleneubank/claude-code/spec-best-practices"><img src="https://agentmods.dev/badge/skills/alleneubank/claude-code/spec-best-practices/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/alleneubank/claude-code/spec-best-practices"><img src="https://agentmods.dev/badge/skills/alleneubank/claude-code/spec-best-practices.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 31 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 933 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.

Model	Per session	Once invoked
Fable 5.1	$0.00031	$0.00933
Opus 5.5	$0.00012	$0.00373
Sonnet 5.5	$0.00006	$0.00187
Haiku 4.5	$0.00003	$0.00093

Measured 2mo ago against content hash ee93094cd5b8, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

spec-best-practices 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 2mo 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.

.claude/skills/spec-best-practices/SKILL.md · 64 lines

How it starts

The opening of the file, as written. The whole thing — 64 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Naming

Always SPEC.md. No exceptions for the primary spec file. Not feature.spec.md, not SPEC-feature.md.

Supporting documents linked from a SPEC.md TOC may use descriptive names (e.g., commands.spec.md), but only when a root SPEC.md exists and links to them.

Placement

Specs are colocated with the code they describe: root SPEC.md for project scope, apps/foo/SPEC.md for app scope, packages/bar/SPEC.md for package scope.

Avoid spec/, docs/specs/, and docs/plans/ directories. Prefer colocated SPEC.md files.
Plan documents are ephemeral. Absorb durable decisions into the relevant SPEC.md and delete the plan doc.
When a spec gets long, add a TOC linking to adjacent supporting files (./commands.spec.md, etc.). Supporting files live alongside the SPEC.md, not in a subdirectory.

Content

Specs are freeform markdown. No rigid template, no YAML frontmatter, no required section ordering. These elements must be present:

Problem and solution -- narrative context for why this system/feature exists. Lead with the problem.

Domain model -- types, relationships, data flow. For retroactive specs, derive from inspected code.

Requirements with REQ-* IDs -- every behavioral requirement gets a stable identifier. Format: REQ-{DOMAIN}-{NNN} (e.g., REQ-AUTH-001). Append-only; never renumber. Each requirement is testable and traceable.

Invariants -- conditions that must always hold.

Non-goals -- explicit scope boundary. What this spec intentionally does not cover.

Acceptance criteria -- markdown checklist, not prose:

- [ ] Auth endpoint returns JWT with tier claim
- [ ] Rate limiter rejects >100 req/min per IP

Risk tags (conditional) -- flag high-risk items (schema migrations, auth changes, public API contracts, infra changes) when those risks exist or the ADF PLAN gate requires approval.

Test traceability (conditional) -- REQ-* to test file:line mapping. Added during/after TDD, not at initial authoring.

Read the full file on GitHub · 64 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.

2mo ago First seen · 64 lines · 31 tokens per session scan A ee93094cd5b8

Subscribe to this mod's changes

spec-best-practices is a skill published in the GitHub repository alleneubank/claude-code (49 stars, last pushed 4mo ago), licensed Apache-2.0. It adds 31 tokens to every session and 933 once invoked, about $0.0001 per session on Opus 5.5. 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.

Writing and docs

spec-best-practices next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
spec-best-practicesalleneubank/claude-code	Skill	49	4mo ago	Apache-2.0	A	31	Claude Code
imagegenopenai/codex	Skill	133k	yesterday	Apache-2.0	A	113	Codex
playwright-climicrosoft/playwright	Skill	99k	yesterday	Apache-2.0	A	19	Claude Code
local-ai-agentsmicrosoft/ai-agents-for-beginners	Skill	79k	4d ago	MIT	A	200	Claude Code, Codex
systematic-debuggingobra/superpowers	Skill	313k	3d ago	MIT	A	21	Claude Code
next-cache-components-adoptionvercel/next.js	Skill	143k	yesterday	MIT	A	95	Claude Code
next-partial-prefetching-adoptionvercel/next.js	Skill	143k	yesterday	MIT	A	103	Claude Code

claude-code: Skill for Claude Code