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.
npx skills add OKHP3/skillz --skill c4-codebase-architecturegit clone --depth 1 https://github.com/OKHP3/skillzWrote 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.
[](https://agentmods.dev/skills/okhp3/skillz/c4-codebase-architecture)<a href="https://agentmods.dev/skills/okhp3/skillz/c4-codebase-architecture"><img src="https://agentmods.dev/badge/skills/okhp3/skillz/c4-codebase-architecture/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/okhp3/skillz/c4-codebase-architecture"><img src="https://agentmods.dev/badge/skills/okhp3/skillz/c4-codebase-architecture.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00047 | $0.03046 |
| Opus 5.5 | $0.00019 | $0.01218 |
| Sonnet 5.5 | $0.00009 | $0.00609 |
| Haiku 4.5 | $0.00005 | $0.00305 |
Grade A, and why
c4-codebase-architecture 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 1mo 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.
This is a copy
100% identical to c4-codebase-architecture — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 539 lines — stays where its author put it; the contents beside it link to each section on GitHub.
C4 Model Codebase Documentation Skill
Purpose
This skill helps an agent inspect a codebase and produce useful C4-style architecture documentation. It should combine evidence from the repository with targeted follow-up questions whenever code inspection alone is not enough to determine system boundaries, responsibilities, runtime topology, or business intent.
The skill should be pragmatic rather than dogmatic. The goal is not to force every repository into a perfect set of four diagrams, but to produce the clearest possible architecture view at the right level of detail.
When to use this skill
Use this skill when the user wants to:
- understand the architecture of an existing codebase
- produce C4 documentation for a repository
- generate a system context, container, or component view
- onboard new engineers with architecture docs
- reverse engineer system structure from code and infrastructure definitions
- compare intended architecture with implemented architecture
This skill works best when the repository includes at least some of the following:
- source code
- infrastructure as code
- deployment descriptors
- README or docs
- API specifications
- CI/CD configuration
- test suites
What this skill should produce
The skill should aim to produce some or all of the following, depending on what the codebase supports:
-
System Context
- the system under study
- human users or personas
- external systems, APIs, providers, or dependencies
- key relationships
-
Container view
- main deployable or runnable units
- databases, queues, frontends, APIs, workers, serverless functions, data stores
- protocols and interactions between them
-
Component view
- major internal components within a selected container
- their responsibilities and relationships
-
Supporting narrative
- assumptions made from code inspection
- unresolved ambiguities
- questions for the user
- notable architectural risks or mismatches
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.
- 1mo ago First seen · 539 lines · 47 tokens per session scan A 69c37c26f2e5
c4-codebase-architecture is a skill published in the GitHub repository OKHP3/skillz (3 stars, last pushed yesterday), licensed MIT. It adds 47 tokens to every session and 3,046 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 100% identical to c4-codebase-architecture, differing in 0 lines, and is treated as a copy.
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