What is plugin-builder?

A checklist and workflow for checking a coding-agent plugin before release. It examines the package structure, included skills, hooks, integrations, and validation evidence.

Use it to scaffold, convert, audit, harden, or prepare a plugin package for release.

It helps find missing paths, unsafe boundaries, and unproven release claims before the plugin is distributed.

plugin-builder — Skill for Codex by jscraik

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 jscraik/Agent-Skills --skill plugin-builder

Clone the repo

git clone --depth 1 https://github.com/jscraik/Agent-Skills

Made for: Codex.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/jscraik/agent-skills/plugin-builder/github.svg)](https://agentmods.dev/skills/jscraik/agent-skills/plugin-builder)

Your own site

<a href="https://agentmods.dev/skills/jscraik/agent-skills/plugin-builder"><img src="https://agentmods.dev/badge/skills/jscraik/agent-skills/plugin-builder/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/jscraik/agent-skills/plugin-builder"><img src="https://agentmods.dev/badge/skills/jscraik/agent-skills/plugin-builder.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 42 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,281 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.

Model	Per session	Once invoked
Fable 5.1	$0.00042	$0.01281
Opus 5	$0.00021	$0.00641
Sonnet 5	$0.00008	$0.00256
Haiku 4.5	$0.00004	$0.00128

Measured 8d ago against content hash 5b0f6127a786, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

plugin-builder 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 8d ago.

The scan reads SKILL.md. This mod also ships 4 executable files (scripts/check_plugin_builder_template_drift.py, scripts/plugin_builder.py, scripts/render_plugin_builder_templates.py, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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/plugin-factory/skills/code_quality_review/plugin-builder/SKILL.md · 172 lines

How it starts

The opening of the file, as written. The whole thing — 172 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Plugin Builder

Philosophy

Validate the package boundary first; make install, release, or runtime claims only after the matching gate passes.

When to Use

Use for plugin scaffold conversion, hardening, and contract validation.

Route elsewhere:

first shell only -> [[plugin-creator]]
install/discovery -> [[plugin-installer]]

Inputs

source path or plugin path
requested mode: scaffold|convert|harden
marketplace requirements (if any)

Execution Boundaries

Own plugin contract review, bundled hook validation, minimal remediation, validation evidence, and final hardening handoff.
Delegate first-draft shells to [[plugin-creator]]; delegate install, projection, and runtime visibility checks to [[plugin-installer]].
Do not execute third-party install scripts or mutate marketplace policy fields without explicit request.
Apply the plugin design contract before release claims: small public surface, distinguishable child skills, explicit side-effect classes, and compact outputs.

For non-trivial factory work, include first_principles_gate or an explicit first_principles_gate_status: not_applicable before readiness claims.

Outputs

Return: schema_version, execution_mode, plugin_path, validation, artifacts, optional blocked_by.

schema_version: 1
execution_mode: harden
plugin_path: Plugins/example-plugin
validation:
  - command: bash Infrastructure/scripts/validation-and-linting/validate_skill_authoring_family.sh
    status: pass
artifacts:
  - Plugins/example-plugin/.codex-plugin/plugin.json
blocked_by: null

Workflow

Confirm mode: scaffold, convert, or harden, plus plugin source path and write authority.
Inspect .codex-plugin/plugin.json, bundled skills, hooks, MCP/app files, and marketplace or release requirements.
Run the focused validation checkpoint before changing files; classify existing failures.
Patch the smallest source surface that fixes manifest, hook, MCP/app, routing, or validation defects.
Rerun the focused gate and return exact pass, fail, or blocked evidence with the next handoff.

Read the full file on GitHub · 172 lines

Files

What ships with it

19 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.

8d ago First seen · 172 lines · 42 tokens per session scan A 5b0f6127a786

Subscribe to this mod's changes

plugin-builder is a skill published in the GitHub repository jscraik/Agent-Skills (8 stars, last pushed 10d ago), licensed Apache-2.0. It adds 42 tokens to every session and 1,281 once invoked, about $0.0002 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 2026-09-03.

Building agents agent-skills agentic-workflow ai-agents ai-coding-agents ask-cli automation

plugin-builder

Getting it into your agent

Wrote this? Show the measurements

What it costs to keep this loaded

Grade A, and why

Nothing flagged

How it starts

Plugin Builder

Philosophy

When to Use

Inputs

Execution Boundaries

Outputs

Workflow

What ships with it

What this file has done since we first saw it

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