explain-codebase

A guide for learning an unfamiliar software repository by mapping its technology, folders, entry points, modules, and data flow.

In plain words
What is it for?
Use it when joining a project or starting work in a repository you do not know. It helps find the run and test commands, important files, and the path data takes through the system.
Why use it?
It replaces a vague first impression with a practical map of where the program starts, how parts depend on one another, and where common concerns are handled.

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/khaledsaeed18/dotclaude/explain-codebase
Any agent
npx skills add KhaledSaeed18/dotclaude --skill explain-codebase
Clone the repo
git clone --depth 1 https://github.com/KhaledSaeed18/dotclaude

Made for: Claude Code, Codex.

Per session 44 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 541 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 $0.00044 $0.00541
Opus 5 $0.00022 $0.00270
Sonnet 5 $0.00009 $0.00108
Haiku 4.5 $0.00004 $0.00054

Measured yesterday against content hash d73aa1d88b85, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

explain-codebase 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.

.claude-plugin/plugins/engineering/skills/explain-codebase/SKILL.md · 39 lines

How it starts

The opening of the file, as written. The whole thing — 39 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Build a navigable map of this repository so the reader can find their way around and start contributing. Work from evidence in the repo, not assumptions about the stack.

Orient first

  • Identify the project type and stack from manifests and config (e.g. package.json, pyproject.toml, go.mod, Cargo.toml, pom.xml, Gemfile, Dockerfiles, CI config). Note the build, test, and run commands.
  • Read the README, docs, and any CONTRIBUTING or architecture notes before reading code, but verify their claims against the tree rather than trusting them blindly.
  • Get the shape of the tree: the top-level directories and what each is responsible for.

Map the architecture

  • Find the entry points: CLI mains, server bootstraps, route registrations, scheduled jobs, queue consumers, lambda/handler exports, UI roots. List them with file:line.
  • Identify the layers / modules and how they depend on each other (e.g. interface → service/domain → data access → external integrations). Note the boundaries that matter.
  • Locate cross-cutting concerns: config/env loading, auth, logging, error handling, database/connection setup, feature flags.

Trace the data flow

  • Pick one or two representative operations (or whatever the user asked to focus on) and follow them end to end: input → validation → core logic → persistence/external calls → response.
  • Show each path as a short sequence of file:line hops the reader can click through.
  • Call out where state lives (databases, caches, queues, external services) and how it's accessed.

Report

Produce, concisely:

  1. Summary: one paragraph on what this project is and does.
  2. Architecture map: the layers/modules and their responsibilities.
  3. Entry points: where execution starts, with paths.
  4. Key flows: the traced paths.
  5. Conventions & gotchas: naming, patterns, where to add a new feature, anything surprising.
  6. Where to look next: the 3 to 5 files most worth reading first.

Prefer precise file:line references over prose. Flag anything you were unsure about rather than guessing.

Read the full file on GitHub · 39 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 · 39 lines · 44 tokens per session scan A d73aa1d88b85

Subscribe to this mod's changes

explain-codebase is a skill published in the GitHub repository KhaledSaeed18/dotclaude (4 stars, last pushed 7d ago), licensed MIT. It adds 44 tokens to every session and 541 once invoked, about $0.0002 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.