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plugin-best-practices

plugin-best-practices is a skill for Codex from Casper-Studios/casper-marketplace. It costs 34 tokens per session (284 once invoked), scanned A, original, MPL-2.0.

Guidance for designing focused, installable packages of agent skills. It explains which skills should be visible to users and which should remain internal.

In plain words
What is it for?
Use it to define plugin boundaries, choose public entry points, split broad plugins, and keep manifests and package contents small.
Why use it?
It helps keep plugins coherent and prevents users from having to understand unnecessary internal parts.

Skill for Codex

Written for Codex: agents/openai.yaml present.

not rated 14repo +1 changed 2mo ago A scan 34 tokens original MPL-2.0

Good fit Use it to define plugin boundaries, choose public entry points, split broad plugins, and keep manifests and package contents small.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/casper-studios/casper-marketplace/plugin-best-practices
View source ↗ Casper-Studios/casper-marketplace casperstudios.com
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 Casper-Studios/casper-marketplace --skill plugin-best-practices
Clone the repo
git clone --depth 1 https://github.com/Casper-Studios/casper-marketplace

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.

agentmods badge for plugin-best-practices

README.md
[![agentmods](https://agentmods.dev/badge/skills/casper-studios/casper-marketplace/plugin-best-practices/github.svg)](https://agentmods.dev/skills/casper-studios/casper-marketplace/plugin-best-practices)
Your own site
<a href="https://agentmods.dev/skills/casper-studios/casper-marketplace/plugin-best-practices"><img src="https://agentmods.dev/badge/skills/casper-studios/casper-marketplace/plugin-best-practices/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 plugin-best-practices

Your own site · 80×15
<a href="https://agentmods.dev/skills/casper-studios/casper-marketplace/plugin-best-practices"><img src="https://agentmods.dev/badge/skills/casper-studios/casper-marketplace/plugin-best-practices.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 34 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 284 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 $0.00034 $0.00284
Opus 5.5 $0.00014 $0.00114
Sonnet 5.5 $0.00007 $0.00057
Haiku 4.5 $0.00003 $0.00028

Measured 2mo ago against content hash c2d6da067c3b, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

plugin-best-practices 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 2mo 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/governance/marketplace/skills/plugin-best-practices/SKILL.md · 26 lines

What it actually says

Plugin Best Practices

Prefer fine-grained plugins that package one coherent installable capability or body of guidance. Consumers install the plugin as a unit instead of assembling cooperating skills or accepting unrelated functionality.

Treat a plugin as an encapsulation boundary. Like a class in object-oriented programming, it exposes a deliberate public interface while hiding implementation details that consumers do not need to understand or invoke.

A plugin can expose one public skill or several independently useful public skills. Those entry points own consumer-facing outcomes while private skills support them without exposing the internal call graph.

Effective Strategies for Focused Agent-Skill Plugins

Follow the guidelines below. Read each linked reference that applies to the plugin design task.

  1. Expose public outcomes while keeping implementation skills private.
  2. Package only the metadata and files that consumers need.
Files

What ships with it

4 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. 2mo ago Changed · +2 lines · -28 tokens per session c2d6da067c3b
  2. 2mo ago First seen · 24 lines · 62 tokens per session scan A 35fa909d72ee

Subscribe to this mod's changes

plugin-best-practices is a skill published in the GitHub repository Casper-Studios/casper-marketplace (14 stars, last pushed yesterday), licensed MPL-2.0. It adds 34 tokens to every session and 284 once invoked, about $0.0001 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 2026-08-30.

Building agents
Related

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plugin-best-practices next to 6 skills from other repositories
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