explain-code

A code-explanation guide that uses everyday comparisons, text diagrams, step-by-step walkthroughs, and common pitfalls. It is for understanding existing code, not changing it.

In plain words
What is it for?
Use it when asking how a function, subsystem, or section of a codebase works.
Why use it?
It makes unfamiliar code and its flow easier to follow without assuming the reader already knows the codebase.

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/helderberto/agent-skills/explain-code
Any agent
npx skills add helderberto/agent-skills --skill explain-code
Clone the repo
git clone --depth 1 https://github.com/helderberto/agent-skills

Made for: Claude Code, Codex.

Per session 62 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 475 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 $0.00062 $0.00475
Opus 5 $0.00031 $0.00237
Sonnet 5 $0.00012 $0.00095
Haiku 4.5 $0.00006 $0.00047

Measured 2d ago against content hash bb90ba5bdb15, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

explain-code 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.

skills/explain-code/SKILL.md · 77 lines

What it actually says

When explaining code, always include:

  1. Start with an analogy: Compare the code to something from everyday life
  2. Draw a diagram: Use ASCII art to show the flow, structure, or relationships
  3. Walk through the code: Explain step-by-step what happens
  4. Highlight a gotcha: What's a common mistake or misconception?

Keep explanations conversational. For complex concepts, use multiple analogies.

Diagram Types

Flow / Control flow:

Input -> [Validate] -> [Process] -> [Save] -> Output
                          |
                       [Error] -> Return 400

Call stack / Sequence:

Client          API           DB
  |--request-->  |             |
  |              |--query----> |
  |              |<--result--- |
  |<-response--  |             |

Tree / Hierarchy:

App
+-- Header
|   +-- Nav
+-- Main
|   +-- Sidebar
|   +-- Content
+-- Footer

State machine:

[Idle] --submit--> [Loading] --success--> [Done]
                       |
                    error|
                   [Failed] --retry--> [Loading]

Data structure:

User {
  id: string
  profile: Profile --> { name, avatar, bio }
  posts: Post[]    --> [{ id, title, body }]
}

Before / After:

Before:               After:
fn()                  fn()
  doA()                 doA()
  doB()                 doB()
  doC()     ->          helpers()
  doD()                   doC()
  doE()                   doD()
                          doE()

Error Handling

  • Code references external files/modules -- read them before explaining
  • Diagram too complex -- split into multiple focused diagrams, each covering one concept
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 · 77 lines · 62 tokens per session scan A bb90ba5bdb15

Subscribe to this mod's changes

explain-code is a skill published in the GitHub repository helderberto/agent-skills (13 stars, last pushed 11d ago), licensed MIT. It adds 62 tokens to every session and 475 once invoked, about $0.0003 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 2026-08-30.

Related

Other skills, from other repositories

code-explanation

Get layered, context-aware explanations of unfamiliar code. Understand what it does, why it was written that way, and how to work with it safely.

DevelopersGlobal/ai-agent-skills · 34 tokens

code-review-and-quality

Conducts multi-axis code review. Use before merging any change. Use when reviewing code written by yourself, another agent, or a human. Use when you need to assess code quality across multiple dimensions before it enters the main branch.

addyosmani/agent-skills · 51 tokens

constraint-driven-development

Establishes a project's quality bar as a written contract and stops agents quietly lowering it. Interviews the user on which dimensions matter, supplies sane default thresholds when they have no number in mind, records everything in CONSTRAINTS.md, and watches the diff for a weakened bar — new @ts-ignore or…

addyosmani/agent-skills · 154 tokens

performance-optimization

Optimizes application performance across frontend, backend, queries, and databases. Use when performance requirements exist, when you suspect performance regressions, when Core Web Vitals or load times need improvement, when N+1 query patterns need fixing, or when profiling reveals bottlenecks.

addyosmani/agent-skills · 59 tokens

api-and-interface-design

Guides stable API and interface design. Use when designing APIs, module boundaries, or any public interface. Use when creating REST or GraphQL endpoints, defining type contracts between modules, or establishing boundaries between frontend and backend.

addyosmani/agent-skills · 49 tokens

code-simplification

Simplifies code for clarity. Use when refactoring code for clarity without changing behavior. Use when code works but is harder to read, maintain, or extend than it should be. Use when reviewing code that has accumulated unnecessary complexity.

addyosmani/agent-skills · 51 tokens