digest:explain

A command for explaining unfamiliar existing code, including how it works, why it was designed that way, or where a bug came from. It combines code reading with the project’s version history.

In plain words
What is it for?
Use it to explain a file, module, function, directory, bug, or the findings from the current investigation to a chosen audience.
Why use it?
It helps a developer understand current behavior and design decisions without reconstructing the history alone. The result is a self-contained HTML explainer with diagrams.

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

Made for: Claude Code, Codex.

Per session 119 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 594 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 $0.00119 $0.00594
Opus 5 $0.00060 $0.00297
Sonnet 5 $0.00024 $0.00119
Haiku 4.5 $0.00012 $0.00059

Measured yesterday against content hash 600ddf4637c1, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

digest:explain 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/digest/skills/explain/SKILL.md · 42 lines

How it starts

The opening of the file, as written. The whole thing — 42 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Explain

Turn unfamiliar code or a finished investigation into a visual explainer. digest covers delta (what changed); explain covers state (what is this, how does it work, why is it like this, where's the bug from).

Usage

$explain                              # explain the current conversation's findings
$explain src/auth/                    # how this module works
$explain handleRetry                  # this function's role in the flow
$explain "why saga pattern here?"     # design rationale via git archaeology
$explain src/ -f "new teammate"       # onboarding tour

Options

Flag Description
-f, --for <audience> Tailor for an audience — free-form string (manager, non-technical, "new teammate", ...). Default: developer

Output is always a self-contained HTML explainer written to the project root (explain-<slug>-<YYYY-MM-DD>.html), plus a one-paragraph conclusion in the terminal.

Process

  1. No arguments → conversation mode (inline, no dispatch): the findings live in the current conversation, so build the explainer directly — read the visual spec at ../../templates/html-explainer.md (relative to this directory), assemble sections from the section library, write the file. If the conversation holds no investigation yet, say so in one line and stop.
  2. Arguments → investigation mode (dispatch): classify the target (existing path → file/module; identifier-like → symbol; else → question) and dispatch the explain agent.

Agent Dispatch (investigation mode only)

Use the companion explain-agent.md in this directory as the agent prompt. Provide it with:

  • Target and target kind (file/module | symbol | question)
  • Audience (free-form string, default developer)
  • Output slug (path → basename; symbol → kebab; question → first ~5 significant words, kebab)
  • The HTML template at ../../templates/html-explainer.md relative to this directory

The agent uses $PROJECT_ROOT (set by the init hook) or falls back to git rev-parse --show-toplevel.

Read the full file on GitHub · 42 lines

Files

What ships with it

1 file 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. yesterday First seen · 42 lines · 119 tokens per session scan A 600ddf4637c1

Subscribe to this mod's changes

digest:explain is a skill published in the GitHub repository shdennlin/agent-plugins (2 stars, last pushed 8d ago), licensed MIT. It adds 119 tokens to every session and 594 once invoked, about $0.0006 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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