c4-code

c4-code is a skill for Claude Code, Codex from rmyndharis/antigravity-skills. It costs 54 tokens per session (1,608 once invoked), scanned A, original, MIT.

A guide for documenting code at the most detailed level of the C4 model, a way to describe software architecture at different levels. It records directories, files, functions, classes, arguments, dependencies, and code structure.

In plain words
What is it for?
Use it to document individual code directories and modules, including function signatures, classes, methods, dependencies, and file locations.
Why use it?
It makes unfamiliar code easier to understand and gives documentation a consistent format. It connects each documented element to its location and related code.

Skill for Claude CodeCodex

About the project

Antigravity Skill Vault is a collection of reusable Agent Skills for Google Antigravity, covering software development, operations, security, and business work. It is for people who want Antigravity agents to follow specialized expertise, personas, and structured workflows. The catalogue skills are entries from this collection.

rmyndharis/antigravity-skills · 1,480 stars · on GitHub

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/rmyndharis/antigravity-skills/c4-code
Any agent
npx skills add rmyndharis/antigravity-skills --skill c4-code
Clone the repo
git clone --depth 1 https://github.com/rmyndharis/antigravity-skills

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for c4-code

README.md
[![agentmods](https://agentmods.dev/badge/skills/rmyndharis/antigravity-skills/c4-code.svg)](https://agentmods.dev/skills/rmyndharis/antigravity-skills/c4-code)
Your own site
<a href="https://agentmods.dev/skills/rmyndharis/antigravity-skills/c4-code"><img src="https://agentmods.dev/badge/skills/rmyndharis/antigravity-skills/c4-code.svg" alt="Measured on agentmods" height="20"></a>
Per session 54 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,608 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 $0.00054 $0.01608
Opus 5 $0.00027 $0.00804
Sonnet 5 $0.00011 $0.00322
Haiku 4.5 $0.00005 $0.00161

Measured 5d ago against content hash 7dd1e22d5917, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

c4-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 5d 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.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

  • c4-code — 100% identical, 1 lines differ
skills/c4-code/SKILL.md · 244 lines

How it starts

The opening of the file, as written. The whole thing — 244 lines — stays where its author put it; the contents beside it link to each section on GitHub.

C4 Code Level: [Directory Name]

Use this skill when

  • Working on c4 code level: [directory name] tasks or workflows
  • Needing guidance, best practices, or checklists for c4 code level: [directory name]

Do not use this skill when

  • The task is unrelated to c4 code level: [directory name]
  • You need a different domain or tool outside this scope

Instructions

  • Clarify goals, constraints, and required inputs.
  • Apply relevant best practices and validate outcomes.
  • Provide actionable steps and verification.

Overview

  • Name: [Descriptive name for this code directory]
  • Description: [Short description of what this code does]
  • Location: [Link to actual directory path]
  • Language: [Primary programming language(s)]
  • Purpose: [What this code accomplishes]

Code Elements

Functions/Methods

  • functionName(param1: Type, param2: Type): ReturnType
    • Description: [What this function does]
    • Location: [file path:line number]
    • Dependencies: [what this function depends on]

Classes/Modules

  • ClassName
    • Description: [What this class does]
    • Location: [file path]
    • Methods: [list of methods]
    • Dependencies: [what this class depends on]

Dependencies

Internal Dependencies

  • [List of internal code dependencies]

External Dependencies

  • [List of external libraries, frameworks, services]

Relationships

Optional Mermaid diagrams for complex code structures. Choose the diagram type based on the programming paradigm. Code diagrams show the internal structure of a single component.

Object-Oriented Code (Classes, Interfaces)

Use classDiagram for OOP code with classes, interfaces, and inheritance:

---
title: Code Diagram for [Component Name]
---
classDiagram
    namespace ComponentName {
        class Class1 {
            +attribute1 Type
            +method1() ReturnType
        }
        class Class2 {
            -privateAttr Type
            +publicMethod() void
        }
        class Interface1 {
            <<interface>>
            +requiredMethod() ReturnType
        }
    }

    Class1 ..|> Interface1 : implements
    Class1 --> Class2 : uses

### Functional/Procedural Code (Modules, Functions)

For functional or procedural code, you have two options:

**Option A: Module Structure Diagram** - Use `classDiagram` to show modules and their exported functions:

```mermaid
---
title: Module Structure for [Component Name]
---
classDiagram
    namespace DataProcessing {
        class validators {
            <<module>>
            +validateInput(data) Result~Data, Error~
            +validateSchema(schema, data) bool
            +sanitize(input) string
        }
        class transformers {
            <<module>>
            +parseJSON(raw) Record
            +normalize(data) NormalizedData
            +aggregate(items) Summary
        }
        class io {
            <<module>>
            +readFile(path) string
            +writeFile(path, content) void
        }
    }

Read the full file on GitHub · 244 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. 5d ago First seen · 244 lines · 54 tokens per session scan A 7dd1e22d5917

Subscribe to this mod's changes

c4-code is a skill published in the GitHub repository rmyndharis/antigravity-skills (1,480 stars, last pushed 1mo ago), licensed MIT. It adds 54 tokens to every session and 1,608 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.

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