codebase-map-index

A method for mapping an unfamiliar software repository so its main parts, entry points, data flow, and useful commands are easy to find.

In plain words
What is it for?
It helps with onboarding, architecture discovery, project indexing, module mapping, and planning work in repositories with multiple applications or services.
Why use it?
Reading every file is slow and can obscure how the project fits together. A focused map gives developers enough context to inspect or change the right areas.

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/yankieldbc2/codex-skills-library/codebase-map-index
Any agent
npx skills add YankielDBC2/codex-skills-library --skill codebase-map-index
Clone the repo
git clone --depth 1 https://github.com/YankielDBC2/codex-skills-library

Made for: Claude Code, Codex.

Per session 27 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 289 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 $0.00027 $0.00289
Opus 5 $0.00014 $0.00144
Sonnet 5 $0.00005 $0.00058
Haiku 4.5 $0.00003 $0.00029

Measured 2d ago against content hash b13ce8978eb4, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

codebase-map-index 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 2d 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.

.agents/skills/codebase-map-index/SKILL.md · 48 lines

What it actually says

Codebase Map Index

Goal

Create a useful map of a repository without reading every file unnecessarily.

When to use

Use for onboarding, architecture discovery, project indexing, module mapping, and planning future changes.

When not to use

Do not use when the user asks for a small targeted code change and the relevant files are obvious.

Inputs

Inspect README, package manifests, routing entry points, app entry points, config files, major folders, and existing docs.

Workflow

  1. Identify frameworks, languages, and package managers.
  2. Locate app entry points and routing boundaries.
  3. Map major folders by responsibility.
  4. Identify data flow, API boundaries, and persistence boundaries.
  5. Record validation commands and local run commands.
  6. Note risky or unclear areas.
  7. Create or update PROJECT_INDEX.md if requested.

Quality bar

A good map helps a future agent make targeted changes without scanning the entire repo.

Validation

Run lightweight commands such as package scripts listing, tests, typecheck, or build only when useful and safe.

Final response

Report the map, important files, commands discovered, and recommended next inspection targets.

Files

What ships with it

4 files 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. 2d ago First seen · 48 lines · 27 tokens per session scan A b13ce8978eb4

Subscribe to this mod's changes

codebase-map-index is a skill published in the GitHub repository YankielDBC2/codex-skills-library (10 stars, last pushed 1mo ago), licensed MIT. It adds 27 tokens to every session and 289 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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