create-plugin

A guide for creating a Marko plugin, which changes the inputs or results of a public class method without replacing the whole class. Plugins are found automatically in a module’s source directory.

In plain words
What is it for?
Use it to change method arguments or return values, stop a method early, add logging, observe calls, or chain several method changes.
Why use it?
It provides a focused way to add validation, logging, caching, or transformations while leaving the original class in place.

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/marko-php/marko/create-plugin
Any agent
npx skills add marko-php/marko --skill create-plugin
Clone the repo
git clone --depth 1 https://github.com/marko-php/marko

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 1,616 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 $0.01616
Opus 5 $0.00060 $0.00808
Sonnet 5 $0.00024 $0.00323
Haiku 4.5 $0.00012 $0.00162

Measured yesterday against content hash 1f1e9604eb02, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

create-plugin 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.

packages/claude-plugins/plugins/marko-skills/skills/create-plugin/SKILL.md · 154 lines

How it starts

The opening of the file, as written. The whole thing — 154 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Create a Marko Plugin

This skill is the canonical specification for a Marko plugin. Do not inspect existing plugins in this project to infer structure — siblings may have drifted from spec. Copy the templates from assets/ verbatim, substitute placeholders, and stop.

A plugin is a class that intercepts the input or output of a public method on any other class — without replacing that class. Plugins are Marko's fine-grained extensibility primitive. They are auto-discovered from any module's src/ directory; no manual registration is needed.

When to use

Use a plugin when the user wants to modify arguments to, or the result from, a public method on a class without rewriting or subclassing it. Common cases:

  • Enrich a return value
  • Validate or transform inputs before the method runs
  • Short-circuit (cache hit, guard, redirect)
  • Log or observe calls
  • Chain transformations across modules

For total replacement of a class, use a Preference instead — that is a separate skill (marko-create-preference). Plugins and Preferences are complementary; only Preferences swap entire implementations.

Plugin model — two timings only

Marko supports exactly two plugin types. A third type that wraps the call is intentionally absent — anything it could do is expressed as a Before (short-circuit) or After (result transformation), keeping the call stack debuggable.

Attribute When What it does
#[Before] Before the target method Modify args, short-circuit, or pass through
#[After] After the target method Receive and modify the return value

Before return semantics

Return value Effect
null Pass-through — original method runs with original args
array Replace arguments — original method runs with these args
Any other non-null value Short-circuit — original method is NOT called

Read the full file on GitHub · 154 lines

Files

What ships with it

2 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. yesterday First seen · 154 lines · 119 tokens per session scan A 1f1e9604eb02

Subscribe to this mod's changes

create-plugin is a skill published in the GitHub repository marko-php/marko (393 stars, last pushed 3d ago), licensed MIT. It adds 119 tokens to every session and 1,616 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 2026-08-30.

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