plan

A skill for turning a feature specification into a detailed implementation plan. It checks the specification, project settings, acceptance criteria, dependencies, risks, and possible parallel work.

In plain words
What is it for?
Use it when you need a plan document for a feature, including task breakdowns, dependencies, effort estimates, and risks.
Why use it?
It breaks a large feature request into ordered tasks so the development work is easier to organize and review.

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/mountainunicorn/add/plan
Any agent
npx skills add MountainUnicorn/add --skill plan
Clone the repo
git clone --depth 1 https://github.com/MountainUnicorn/add

Made for: Claude Code, Codex.

Per session 14 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,885 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 $0.00014 $0.03885
Opus 5 $0.00007 $0.01943
Sonnet 5 $0.00003 $0.00777
Haiku 4.5 $0.00001 $0.00388

Measured yesterday against content hash b8b1f88eff26, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

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 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.

core/skills/plan/SKILL.md · 544 lines

How it starts

The opening of the file, as written. The whole thing — 544 lines — stays where its author put it; the contents beside it link to each section on GitHub.

ADD Plan Skill v{{VERSION}}

Create a detailed implementation plan from a feature specification. This skill analyzes acceptance criteria, breaks down work into manageable tasks, identifies parallelizable work, and estimates effort.

Overview

The Plan skill transforms a specification into an actionable implementation roadmap. It produces a plan document (docs/plans/{feature}-plan.md) that guides development work and enables:

  • Task breakdown and prioritization
  • Effort estimation
  • Dependency identification
  • Parallelization opportunities
  • Risk assessment
  • Resource allocation

The plan bridges the gap between "what to build" (spec) and "how to build it" (implementation).

Pre-Flight Checks

  1. Verify spec exists and is complete

    • Read spec file from argument
    • Verify YAML frontmatter is valid
    • Extract feature name, version, status
    • Verify acceptance criteria are defined
    • Verify user test cases are defined (if applicable)
  2. Load project configuration

    • Read .add/config.json
    • Load team size (solo, small, large)
    • Load tech stack
    • Load constraints (timeline, budget, etc.)
    • Load parallelization preferences
  3. Analyze dependencies

    • Identify upstream work needed
    • Check for blockers
    • Identify integration points
  4. Check for existing plan

    • Look for docs/plans/{feature}-plan.md
    • If exists, ask user: overwrite or update?
    • Preserve previous efforts if updating
  5. Check for session handoff — per the Session-Handoff Preflight in ${CLAUDE_PLUGIN_ROOT}/references/skill-epilogue.md

Execution Steps

Step 1: Analyze Acceptance Criteria

For each acceptance criterion:

  1. Understand the requirement

    • Read AC text carefully
    • Identify what "done" means
    • Note any explicit constraints
  2. Decompose into tasks

    • What code needs to be written?
    • What tests need to be written?
    • What configuration changes?
    • What documentation?
    • What other work (DB migrations, etc.)?

Read the full file on GitHub · 544 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. yesterday First seen · 544 lines · 14 tokens per session scan A b8b1f88eff26

Subscribe to this mod's changes

plan is a skill published in the GitHub repository MountainUnicorn/add (11 stars, last pushed 1mo ago), licensed MIT. It adds 14 tokens to every session and 3,885 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.