spec-plan

spec-plan is a skill for Claude Code, Codex from H2Sxxa/spec-coding-skills. It costs 78 tokens per session (1,909 once invoked), scanned A, original, MIT.

A planning tool that turns a vague software request into a clear description of what to build, what is out of scope, and how to tell when it is finished.

In plain words
What is it for?
Use it to clarify requirements, write implementation-ready specifications, define validation steps, and create a guarded coding plan.
Why use it?
It reduces guesswork before coding starts, especially around missing details, edge cases, and acceptance criteria.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to clarify requirements, write implementation-ready specifications, define validation steps, and…

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Install with agentmods
npx agentmods add skills/h2sxxa/spec-coding-skills/spec-plan
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 H2Sxxa/spec-coding-skills --skill spec-plan
Clone the repo
git clone --depth 1 https://github.com/H2Sxxa/spec-coding-skills

Made for: Claude Code, Codex.

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 spec-plan

README.md
[![agentmods](https://agentmods.dev/badge/skills/h2sxxa/spec-coding-skills/spec-plan.svg)](https://agentmods.dev/skills/h2sxxa/spec-coding-skills/spec-plan)
Your own site
<a href="https://agentmods.dev/skills/h2sxxa/spec-coding-skills/spec-plan"><img src="https://agentmods.dev/badge/skills/h2sxxa/spec-coding-skills/spec-plan.svg" alt="Measured on agentmods" height="20"></a>
Per session 78 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,909 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 $0.00078 $0.01909
Opus 5 $0.00039 $0.00955
Sonnet 5 $0.00016 $0.00382
Haiku 4.5 $0.00008 $0.00191

Measured 6d ago against content hash 1a4cd568be96, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

spec-plan 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.

skills/spec-plan/SKILL.md · 192 lines

How it starts

The opening of the file, as written. The whole thing — 192 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Spec Planning

Use this skill when the task is still fuzzy and the agent should define success before implementation begins.

This skill turns a request into a practical spec. The goal is not project-management theater. The goal is to make coding safer and faster by clarifying scope, constraints, edge cases, validation, and what counts as done.

Bundled resources

  • references/self-check.md defines the self-check checklist, ambiguity handling, blocking-question rules, execution guardrails, and change-control policy.
  • references/output-template.md defines the preferred implementation-ready spec output shape for persisted task specs and complex conversation plans.

Read references/self-check.md before finalizing a persisted task spec, handing a plan to implementation, or when ambiguity could lead to execution-time guessing.

Use references/output-template.md when writing a persisted task spec or a complex plan that needs stable structure.

Repository preference override

Before doing anything else, look for a SPEC.md in the target repository root.

If it exists, treat it as the repository-specific preference layer for:

  • shared validation rules
  • environment and configuration constraints that affect planning
  • knowledge-base location
  • cross-skill workflow conventions

If it is missing, use the built-in defaults for this skill series instead of blocking on the missing file.

If it is partial, use the fields it defines and fall back to defaults for the rest.

Built-in defaults

When no repository root SPEC.md is available, use these defaults:

  • validation behavior: prefer discoverable repository tooling; if no validation commands are discoverable, say validation is not configured yet
  • knowledge-base location: docs/knowledge-base/
  • task spec location: docs/specs/<slug>.md
  • task execution mode: keep the plan in conversation for small, well-bounded tasks; persist it for complex, risky, or multi-turn work
  • context retrieval: query spec-index for relevant decisions, constraints, setup notes, pitfalls, and validation rules before planning non-trivial work
  • self-check: apply references/self-check.md before implementation handoff

Read the full file on GitHub · 192 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. 6d ago First seen · 192 lines · 78 tokens per session scan A 1a4cd568be96

Subscribe to this mod's changes

spec-plan is a skill published in the GitHub repository H2Sxxa/spec-coding-skills (3 stars, last pushed 1mo ago), licensed MIT. It adds 78 tokens to every session and 1,909 once invoked, about $0.0004 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.