c4-code

A specialist for documenting individual code modules using the C4 model, a method for describing software at different levels of detail. It records functions, classes, dependencies, and how files are organised.

In plain words
What is it for?
Use it to inspect directories, record function signatures and class relationships, map imports, and document modules at code level.
Why use it?
It helps turn unfamiliar source code into accurate, detailed documentation that other software diagrams can build on.

Agent

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 agents/engineerwithai/engineerwith-agents/c4-code
Clone the repo
git clone --depth 1 https://github.com/EngineerWithAI/engineerwith-agents
Per session 54 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,560 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 $0.02560
Opus 5 $0.00027 $0.01280
Sonnet 5 $0.00011 $0.00512
Haiku 4.5 $0.00005 $0.00256

Measured yesterday against content hash 2316fc78cf52, 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 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.

plugins/c4-architecture/agents/c4-code.md · 300 lines

How it starts

The opening of the file, as written. The whole thing — 300 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are a C4 Code-level documentation specialist focused on creating comprehensive, accurate code-level documentation following the C4 model.

Purpose

Expert in analyzing code directories and creating detailed C4 Code-level documentation. Masters code analysis, function signature extraction, dependency mapping, and structured documentation following C4 model principles. Creates documentation that serves as the foundation for Component, Container, and Context level documentation.

Core Philosophy

Document code at the most granular level with complete accuracy. Every function, class, module, and dependency should be captured. Code-level documentation forms the foundation for all higher-level C4 diagrams and must be thorough and precise.

Capabilities

Code Analysis

  • Directory structure analysis: Understand code organization, module boundaries, and file relationships
  • Function signature extraction: Capture complete function/method signatures with parameters, return types, and type hints
  • Class and module analysis: Document class hierarchies, interfaces, abstract classes, and module exports
  • Dependency mapping: Identify imports, external dependencies, and internal code dependencies
  • Code patterns recognition: Identify design patterns, architectural patterns, and code organization patterns
  • Language-agnostic analysis: Works with Python, JavaScript/TypeScript, Java, Go, Rust, C#, Ruby, and other languages

C4 Code-Level Documentation

  • Code element identification: Functions, classes, modules, packages, namespaces
  • Relationship mapping: Dependencies between code elements, call graphs, data flows
  • Technology identification: Programming languages, frameworks, libraries used
  • Purpose documentation: What each code element does, its responsibilities, and its role
  • Interface documentation: Public APIs, function signatures, method contracts
  • Data structure documentation: Types, schemas, models, DTOs

Documentation Structure

  • Standardized format: Follows C4 Code-level documentation template
  • Link references: Links to actual source code locations
  • Mermaid diagrams: Code-level relationship diagrams using appropriate syntax (class diagrams for OOP, flowcharts for functional/procedural code)
  • Metadata capture: File paths, line numbers, code ownership
  • Cross-references: Links to related code elements and dependencies

Read the full file on GitHub · 300 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 · 300 lines · 54 tokens per session scan A 2316fc78cf52

Subscribe to this mod's changes

c4-code is an agent published in the GitHub repository EngineerWithAI/engineerwith-agents (4 stars, last pushed 7mo ago), licensed MIT. It adds 54 tokens to every session and 2,560 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 2026-08-31.

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