writing-plans

writing-plans is a skill for Claude Code, Codex from wazimmerman/zimster. It costs 26 tokens per session (914 once invoked), scanned A, original, MIT.

A method for turning an agreed mission into a short implementation plan made of vertical slices. A vertical slice follows one user-visible path through the needed parts of a system, from input to outcome.

In plain words
What is it for?
Use it to write implementation plans with requirements, evidence, risk level, Git policy, and proof obligations. It helps decide which end-to-end slices to build and how to verify each one.
Why use it?
It prevents plans from becoming disconnected lists of files or technical layers with no proof that the feature works. It also makes risks, acceptance evidence, and Git boundaries explicit before coding starts.

Skill for Claude CodeCodex

Written for Claude Code and Codex: shipped in a Claude Code plugin, but also agents/openai.yaml present.

Part of the zimster plugin — 12 skills, 1 command, 4 agents, 1 hook shipped together

Good fit Use it to write implementation plans with requirements, evidence, risk level, Git policy, and proof obligations. It helps decide which end-to-end slices to build and how to verify each one.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/wazimmerman/zimster/writing-plans
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 wazimmerman/zimster --skill writing-plans
Clone the repo
git clone --depth 1 https://github.com/wazimmerman/zimster

Made for: Claude Code, Codex.

Or install zimster, the plugin that ships this one along with the rest of its 12 skills, 1 command, 4 agents, 1 hook.

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 writing-plans

README.md
[![agentmods](https://agentmods.dev/badge/skills/wazimmerman/zimster/writing-plans/github.svg)](https://agentmods.dev/skills/wazimmerman/zimster/writing-plans)
Your own site
<a href="https://agentmods.dev/skills/wazimmerman/zimster/writing-plans"><img src="https://agentmods.dev/badge/skills/wazimmerman/zimster/writing-plans/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 writing-plans

Your own site · 80×15
<a href="https://agentmods.dev/skills/wazimmerman/zimster/writing-plans"><img src="https://agentmods.dev/badge/skills/wazimmerman/zimster/writing-plans.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 26 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 914 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 $0.00026 $0.00914
Opus 5 $0.00013 $0.00457
Sonnet 5 $0.00005 $0.00183
Haiku 4.5 $0.00003 $0.00091

Measured 10d ago against content hash cf418d5eb0d9, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

writing-plans 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 10d 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/zimster/skills/writing-plans/SKILL.md · 120 lines

How it starts

The opening of the file, as written. The whole thing — 120 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Writing Plans

A plan is an execution contract, not a typing transcript. Preserve semantic precision while removing procedural repetition.

Plan vertical slices

A vertical slice produces observable behavior through every needed component. Prefer “request → validation → persistence → API → UI state” over disconnected model/backend/frontend tasks.

A slice earns a boundary when it has an observable outcome, distinct risk/seam, focused RED-GREEN-REFACTOR proof, and meaningful commit boundary. Do not split setup, config, docs, or one type definition into separate task gates.

Required structure

# <Feature> Implementation Plan

## Mission and constraints
Binding requirements only, each with a stable requirement ID.

## Requirement-to-evidence matrix
For every stable requirement ID: authoritative text/source, implementation
locations, evidence references, environment or harness scope, unavailable
proof, status, and intended acceptance claims.

## Profile and rationale
Micro | Standard | High risk, six dimensions, hard triggers.

## Git and durable-state policy
Default/feature branch behavior, worktree need, commit permission/boundaries,
and deterministic Git-local durable-state triggers.

## Architecture and ownership
Files/components, authoritative state, interfaces, cancellation/cleanup.

## Verification commands
Repository-declared canonical focused, affected, integration, and full gates.

## Slice 1: <observable result>
- Scope/files and interface contracts
- Load-bearing behaviors
- Meaningful RED proof for each behavior
- Minimal implementation direction
- GREEN/regression/mutation evidence
- Risk trigger/review lenses
- Commit boundary

## Integration and completion
Complete change review including untracked files, final gates,
external/hardware/manual evidence, documentation, semantic review package,
candidate-completion gate, and honest state.

Profile rules

  • Micro: all dimensions Low, one slice, no public contract/hard trigger.
  • Standard: one or more Medium dimensions, no High/hard trigger.
  • High risk: any High dimension or hard trigger.

Read the full file on GitHub · 120 lines

Files

What ships with it

1 file 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. 10d ago First seen · 120 lines · 26 tokens per session scan A cf418d5eb0d9

Subscribe to this mod's changes

writing-plans is a skill published in the GitHub repository wazimmerman/zimster (2 stars, last pushed 9d ago), licensed MIT. It adds 26 tokens to every session and 914 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 2026-08-31.

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