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Claude Skill

Codebase Onboarding Doc Builder

Generates an audience-aware onboarding doc for an unfamiliar codebase — architecture, setup, conventions, what's load-bearing.

Download skill (.zip)Or download whole pack

What it does

Analyzes a repo and produces an onboarding document tailored to the audience (junior IC, senior IC, contractor, tech lead). Surfaces architecture, key files, local setup, conventions, and the parts of the codebase a new contributor needs to be careful around. Different from just "summarize this repo" — it produces something a real onboardee can actually act from.

When to use

  • ✓New hire joining the team
  • ✓Contractor coming on for a defined scope
  • ✓A repo just got handed off and the original maintainer is gone
  • ✓You inherited a service and need to onboard yourself

When not to use

  • ✗The repo is well-documented already — don't duplicate
  • ✗Greenfield project where there's not enough to document yet

Install

Download the .zip, then unzip into your Claude skills folder.

mkdir -p ~/.claude/skills
unzip ~/Downloads/codebase-onboarding-doc-builder.zip -d ~/.claude/skills/

# Restart Claude Code session.
# Skill is now available — Claude will use it when relevant.

SKILL.md

SKILL.md
---
name: codebase-onboarding-doc-builder
description: Use when generating onboarding documentation for a codebase. Triggers on "onboarding doc", "new hire docs", "codebase walkthrough", or "ramp-up plan for engineer".
---

# Codebase Onboarding Doc Builder

A good onboarding doc is the thing a new engineer wishes they'd had on day 1. Not a wiki dump. Not a chronological history. A working map.

## Required inputs

1. **The repo or directory** — actual files, not a summary
2. **Audience** — junior IC / senior IC / contractor / tech lead. Affects depth.
3. **Scope** — full codebase or a specific module
4. **Time to first contribution** — what's "ramped up" mean for this person? (PR merged in week 1? Owning a feature in month 1?)

## Sections to produce

### 1. What this service does (≤3 sentences)
Plain language. What it does for the user, not how it works.

### 2. Architecture in one diagram
Text-based diagram (Mermaid or ASCII) showing the main pieces, requests, and data flow. Skip the 47-box "complete picture" — show the 6 boxes someone needs to know.

### 3. Local setup that actually works
- Prereqs (versions, accounts, env vars)
- Step-by-step setup, copy-pasteable
- The thing that always breaks (with the fix)
- How to know setup worked (the smoke test)

If you can't verify the steps work, mark which ones are "expected to work but not verified."

### 4. The map of where things live
A small directory inventory with one-line "what's in here, why" per top-level folder. Skip generated, vendored, and config.

### 5. Conventions
Things the codebase does its own way. Not "we use TypeScript" — "we never use default exports; use named." The conventions that, if violated, get a PR comment.

### 6. What's load-bearing
The 3–5 files / functions / patterns that half the codebase depends on. Touch with care.

### 7. What's vestigial
Stuff that looks active but isn't. Old paths kept for one weird customer, deprecated APIs not yet removed, dead feature flags.

### 8. Audience-specific ramp plan
- **Junior IC**: 3 starter tickets in increasing difficulty, with hints
- **Senior IC**: the 2 unowned areas they could meaningfully take over
- **Contractor**: the scope boundary + integration points they need to respect
- **Tech lead**: open architectural questions, recent decisions, the team's current pain

### 9. Where to ask for help
- Real people, by name (with backups)
- Slack channels by topic
- The runbook + on-call rotation
- What questions to ask vs. what questions to figure out first

## Tone

- Match the audience's level — don't explain pointers to a senior, don't skip them for a junior
- Cite file paths, not vague descriptions
- Flag unknowns ("unclear from code, needs SME") rather than guessing
- Update-friendly — write so the next maintainer can edit, not rewrite

Example prompts

Once installed, try these prompts in Claude:

  • Onboarding doc for our payment service, for a senior IC joining next month. [paste repo URL / structure]
  • Quick onboarding for a contractor scoped to the billing module only. They have 2 weeks. [context]
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