Getting it into your agent
This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.
/plugin marketplace add dwmkerr/claude-toolkit/plugin install toolkitWrote 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.
[](https://agentmods.dev/skills/dwmkerr/claude-toolkit/claude-code-plugin-development)<a href="https://agentmods.dev/skills/dwmkerr/claude-toolkit/claude-code-plugin-development"><img src="https://agentmods.dev/badge/skills/dwmkerr/claude-toolkit/claude-code-plugin-development/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.
<a href="https://agentmods.dev/skills/dwmkerr/claude-toolkit/claude-code-plugin-development"><img src="https://agentmods.dev/badge/skills/dwmkerr/claude-toolkit/claude-code-plugin-development.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00054 | $0.01473 |
| Opus 5.5 | $0.00022 | $0.00589 |
| Sonnet 5.5 | $0.00011 | $0.00295 |
| Haiku 4.5 | $0.00005 | $0.00147 |
Grade B, and why
claude-code-plugin-development scanned grade B with 1 finding 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 1mo 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.
Reads agent configuration directoriesmediumAgent snooping
.claude/, .codex/, .gemini/ hold keys, settings and other credentials a mod has no legitimate need for.
| user | `~/.claude/settings.json` | Personal plugins (default) | How it starts
The opening of the file, as written. The whole thing — 212 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Claude Code Plugin Development
Create distributable plugins that bundle commands, agents, skills, hooks, MCP servers, and LSP servers.
Official docs: https://code.claude.com/docs/en/plugins-reference
Quick Reference
You MUST read these references for detailed schemas and examples:
- Plugin Manifest - Complete plugin.json schema
- Plugin Components - Commands, agents, skills, hooks, MCP, LSP
- CLI Commands - Install, uninstall, enable, disable, update
- Debugging - Common issues and troubleshooting
Plugin Structure
my-plugin/
├── .claude-plugin/
│ └── plugin.json # Required manifest
├── commands/ # Slash commands (.md files)
├── agents/ # Subagents (.md files)
├── skills/ # Skills (subdirs with SKILL.md)
├── hooks/
│ └── hooks.json # Hook configuration
├── .mcp.json # MCP server definitions
├── .lsp.json # LSP server configurations
└── scripts/ # Hook and utility scripts
Important: Components go at plugin root, NOT inside .claude-plugin/. Only plugin.json belongs in .claude-plugin/.
Marketplace Structure
A marketplace can contain multiple plugins. The marketplace root has its own .claude-plugin/marketplace.json:
my-marketplace/
├── .claude-plugin/
│ └── marketplace.json # Lists all plugins in this marketplace
├── plugins/
│ ├── plugin-a/
│ │ ├── .claude-plugin/
│ │ │ └── plugin.json
│ │ └── skills/
│ └── plugin-b/
│ ├── .claude-plugin/
│ │ └── plugin.json
│ └── commands/
marketplace.json
{
"name": "my-marketplace",
"owner": {
"name": "author-name"
},
"plugins": [
{
"name": "plugin-a",
"source": "./plugins/plugin-a",
"description": "First plugin description",
"version": "1.0.0"
},
{
"name": "plugin-b",
"source": "./plugins/plugin-b",
"description": "Second plugin description",
"version": "0.2.0"
}
]
}
What ships with it
5 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.
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.
- 1mo ago First seen · 212 lines · 54 tokens per session scan B 23f7bc01c2a4
claude-code-plugin-development is a skill published in the GitHub repository dwmkerr/claude-toolkit (23 stars, last pushed 1mo ago), licensed MIT. It adds 54 tokens to every session and 1,473 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it B with 1 finding (reads agent configuration directories). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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