cover-letter

cover-letter is a skill for Claude Code, Codex from chucklever/cel-kdev. It costs 250 tokens per session (4,820 once invoked), scanned A, original, MIT.

A writing guide for documents that introduce a group of code changes, such as a GitHub pull request description or a Linux kernel patch-series cover letter. These documents explain the overall design and how reviewers should read the changes.

In plain words
What is it for?
Use it when preparing a pull request description, a patch-series introduction, or a merge commit message for related changes.
Why use it?
It helps reviewers understand decisions and dependencies that may not be clear from individual code changes or commit messages.

Skill for Claude CodeCodex

Part of the cel-prose plugin — 5 skills shipped together

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/chucklever/cel-kdev/cover-letter
Any agent
npx skills add chucklever/cel-kdev --skill cover-letter
Clone the repo
git clone --depth 1 https://github.com/chucklever/cel-kdev

Made for: Claude Code, Codex.

Or install cel-prose, the plugin that ships this one along with the rest of its 5 skills.

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 cover-letter

README.md
[![agentmods](https://agentmods.dev/badge/skills/chucklever/cel-kdev/cover-letter.svg)](https://agentmods.dev/skills/chucklever/cel-kdev/cover-letter)
Your own site
<a href="https://agentmods.dev/skills/chucklever/cel-kdev/cover-letter"><img src="https://agentmods.dev/badge/skills/chucklever/cel-kdev/cover-letter.svg" alt="Measured on agentmods" height="20"></a>
Per session 250 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,820 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 $0.00250 $0.04820
Opus 5 $0.00125 $0.02410
Sonnet 5 $0.00050 $0.00964
Haiku 4.5 $0.00025 $0.00482

Measured 4d ago against content hash d0e854abbe04, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

cover-letter 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 4d 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.

plugin/cel-prose/skills/cover-letter/SKILL.md · 397 lines

How it starts

The opening of the file, as written. The whole thing — 397 lines — stays where its author put it; the contents beside it link to each section on GitHub.

cover-letter

How to write the content of a document that introduces a set of changes to the people who will review them, in Chuck's voice. The Linux kernel patch series cover letter is the main case, and the rules below are written against it. A GitHub pull request description and a merge commit message do the same job and take the same rules; "Other surfaces" at the end covers where they differ. Where the cover file lives and how a kernel series is sent (b4/series-send) belong to the series-send and cel-kdev:b4 skills; a reroll's changelog belongs to the cel-prose:version-changelog skill, and a single patch's commit message to the cel-prose:commit-message skill. Load those for the workflow, this for the prose.

What a cover letter is for

The cover directs reviewer attention. It carries what the diffs and the commit messages do not advertise: design choices that span several patches, subtle invariants, ordering constraints, and contracts a later patch relies on. A reviewer reads the cover to learn how to read the series.

So the test for every sentence is whether it earns its place against that purpose. If a reviewer will find its content in the patch it belongs to -- the subject line in the shortlog, the commit message, the diff -- it is redundant here; cut it. The defect the series answers is the exception. State it here even though the fixing patch states it too. The cover is not a summary of the patches; it records the cross-cutting design that no single patch carries.

The cover never enters git history: a part-zero cover is not applied at all, and for a lone patch the same text sits below the "---" that git strips at apply time. It lives only in the review thread. So the cover coordinates the series but never substitutes for a patch's own commit message -- anything a single patch needs to justify itself belongs in that patch, not only in the cover.

Before drafting: sourcing the rationale

The cover carries what the patches do not, so the patches cannot be the only input. Reading the series tells you what it does. It rarely tells you why it exists, and that is the half a reviewer is being asked to accept. Go get it first:

Read the full file on GitHub · 397 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. 4d ago First seen · 397 lines · 250 tokens per session scan A d0e854abbe04

Subscribe to this mod's changes

cover-letter is a skill published in the GitHub repository chucklever/cel-kdev (2 stars, last pushed 3d ago), licensed MIT. It adds 250 tokens to every session and 4,820 once invoked, about $0.0013 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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