feature-documentation

A guide for writing lasting reference pages about software features, including what they do, how they behave, and where they are implemented.

In plain words
What is it for?
It helps engineers document routes, jobs, database tables, configuration, modules, file paths, and important limits under docs/features.
Why use it?
It keeps feature documentation useful and accurate instead of turning it into a progress report or a record of past development work.

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/sflandergan/agentic-coding/feature-documentation
Any agent
npx skills add sflandergan/agentic-coding --skill feature-documentation
Clone the repo
git clone --depth 1 https://github.com/sflandergan/agentic-coding

Made for: Claude Code, Codex.

Per session 16 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 717 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 $0.00016 $0.00717
Opus 5 $0.00008 $0.00358
Sonnet 5 $0.00003 $0.00143
Haiku 4.5 $0.00002 $0.00072

Measured yesterday against content hash df08dd421c60, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

feature-documentation 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/agents/skills/feature-documentation/SKILL.md · 105 lines

How it starts

The opening of the file, as written. The whole thing — 105 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Feature Documentation

Overview

Write durable feature reference documentation for engineers and product readers. A feature doc explains what exists, how it behaves, where it lives, and which boundaries matter. It is not a status report, implementation diary, PR summary, or verification log.

Use this skill whenever creating or updating docs/features/*.md.

Required Style

  • Write in present tense: describe current behavior.
  • Prefer concrete names: routes, job names, table names, config variables, modules, and file paths.
  • Explain ownership boundaries that exist in your project; do not invent roles that the codebase does not actually have.
  • Include only sections that apply to the feature.
  • Keep implementation history out of the doc unless it explains a durable design decision.

Do not include:

  • implementation status such as "implemented", "ready", or "reviewed"
  • dates, commit hashes, branch names, PR numbers, or cleanup notes
  • verification logs or lists of test commands
  • plan/spec file inventories
  • agent handoff language

Document Shape

Use this sample as the default shape. Rename, omit, or add sections only when the feature needs it. If a section does not apply to the feature, omit it.

# <Feature Name> Feature

Briefly describe what this feature adds in durable product/engineering terms. Write this as reference documentation, not as an implementation status report.

## Scope

- User-visible or system capability 1.
- User-visible or system capability 2.
- Important boundary or non-goal if useful.

## APIs

Describe public/internal APIs if the feature adds or changes any.

### Public API

| Method | Route | Purpose |
|---|---|---|
| `GET` | `/api/example` | Describe what the route returns and why it exists. |

### Internal APIs

- `METHOD /internal/example` — purpose and important behavior.

## Background Work / Operational Flows

Describe jobs, scripts, or operational flows when the feature includes any.

- `job-name`
  - What it does.
  - What state it reads/writes.
  - Important scheduling, retry, or idempotency behavior.

## Database State

Describe important tables, fields, uniqueness, and ownership boundaries.

- `table_name`
  - Purpose.
  - Important keys or lifecycle fields.

## Configuration

- `ENV_VAR` — purpose and default if relevant.

## Main Code Locations

- Area: `path/to/file.ts`, `path/to/directory`

Read the full file on GitHub · 105 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 · 105 lines · 16 tokens per session scan A df08dd421c60

Subscribe to this mod's changes

feature-documentation is a skill published in the GitHub repository sflandergan/agentic-coding (2 stars, last pushed 2mo ago), licensed MIT. It adds 16 tokens to every session and 717 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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