how

how is a skill for Claude Code, Codex from minghinmatthewlam/agent-guards. It costs 60 tokens per session (577 once invoked), scanned A, original, MIT.

A codebase exploration and explanation workflow for understanding how a subsystem works. It builds a practical map of the parts, runtime flow, ownership, and layering before changes are made.

In plain words
What is it for?
Use it to answer how code works, explain a subsystem to a new developer, or decide where a feature or responsibility belongs.
Why use it?
Large codebases can make it hard to know where behavior lives or which component should own a change. A structured walkthrough reduces that uncertainty.

Skill for Claude CodeCodex

Written for Claude Code and Codex: user-invocable in frontmatter, but also agents/openai.yaml present. Also seen: mentions subagents.

Part of the pstack plugin — 55 skills, 2 agents shipped together

Good fit Use it to answer how code works, explain a subsystem to a new developer, or decide where a feature or responsibility belongs.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/minghinmatthewlam/agent-guards/how
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.

Any agent
npx skills add minghinmatthewlam/agent-guards --skill how
Clone the repo
git clone --depth 1 https://github.com/minghinmatthewlam/agent-guards

Made for: Claude Code, Codex.

Or install pstack, the plugin that ships this one along with the rest of its 55 skills, 2 agents.

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 how

README.md
[![agentmods](https://agentmods.dev/badge/skills/minghinmatthewlam/agent-guards/how/github.svg)](https://agentmods.dev/skills/minghinmatthewlam/agent-guards/how)
Your own site
<a href="https://agentmods.dev/skills/minghinmatthewlam/agent-guards/how"><img src="https://agentmods.dev/badge/skills/minghinmatthewlam/agent-guards/how/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.

agentmods 80×15 button for how

Your own site · 80×15
<a href="https://agentmods.dev/skills/minghinmatthewlam/agent-guards/how"><img src="https://agentmods.dev/badge/skills/minghinmatthewlam/agent-guards/how.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 60 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 577 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00060 $0.00577
Opus 5.5 $0.00024 $0.00231
Sonnet 5.5 $0.00012 $0.00115
Haiku 4.5 $0.00006 $0.00058

Measured 2d ago against content hash 32b2c1bb8ab2, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

how 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.

plugins/pstack/skills/how/SKILL.md · 37 lines

How it starts

The opening of the file, as written. The whole thing — 37 lines — stays where its author put it; the contents beside it link to each section on GitHub.

How

Explore the codebase to answer "how does X work?" questions. Produce architectural explanations at the level of a senior engineer onboarding onto a subsystem, enough to build a working mental model, not so much that it reads like annotated source code.

Every spawn is a Task subagent with subagent_type: generalPurpose and readonly: true. Explorers use the how explorer line in the ~/.config/pstack/models.md rule (default grok-4.7-xhigh-fast), and every explainer uses the how explainer line (default claude-opus-5-5-xhigh). Set model to that line's value, or to the default if the rule or the line is missing. Leave model unset when the value is auto or inherit-parent. If the Task tool rejects a slug, use the default and say so. If it rejects the default, use the closest valid slug of the same family from its error message.

1. Assess complexity

If the scope is ambiguous, state your interpretation and explore. The user can redirect.

  • Simple (a single module, a small utility, a narrow question such as "how does function X work"): no explorers. Spawn one explainer that explores and explains in one pass, built from references/explainer-prompt.md without the explorer-findings section. Go to step 4.
  • Complex (a subsystem spanning multiple files or services, a cross-cutting feature, a full architectural overview): go to step 2.

When in doubt, take the simple path.

2. Explore (complex only)

Decompose the question into 2 to 4 angles, each a distinct slice of the subsystem. Spawn all explorers in a single message, each with references/explorer-prompt.md and its angle filled in.

3. Synthesize (complex only)

Once all explorers have returned, spawn one explainer with references/explainer-prompt.md and every explorer's findings filled in.

4. Present

Present the explainer's output. Light edits for clarity or context from the conversation are fine. Do not substantially rewrite it.

Output format

The explanation uses the sections defined in references/explainer-prompt.md, dropping any that do not apply: Overview, Key Concepts, How It Works, Where Things Live, Gotchas.

Read the full file on GitHub · 37 lines

Files

What ships with it

3 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 · 37 lines · 60 tokens per session scan A 32b2c1bb8ab2

Subscribe to this mod's changes

how is a skill published in the GitHub repository minghinmatthewlam/agent-guards (47 stars, last pushed 2d ago), licensed MIT. It adds 60 tokens to every session and 577 once invoked, about $0.0002 per session on Opus 5.5. 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 2026-10-14.

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