Borrowing it
Nothing to install: this file belongs to donnfelker/donnfelker-plugin-marketplace. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/donnfelker/donnfelker-plugin-marketplace/main/AGENTS.mdgit clone --depth 1 https://github.com/donnfelker/donnfelker-plugin-marketplaceWrote 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/instructions/donnfelker/donnfelker-plugin-marketplace/agents-md)<a href="https://agentmods.dev/instructions/donnfelker/donnfelker-plugin-marketplace/agents-md"><img src="https://agentmods.dev/badge/instructions/donnfelker/donnfelker-plugin-marketplace/agents-md/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/instructions/donnfelker/donnfelker-plugin-marketplace/agents-md"><img src="https://agentmods.dev/badge/instructions/donnfelker/donnfelker-plugin-marketplace/agents-md.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 | $0.01596 | $0.01596 |
| Opus 5.5 | $0.00638 | $0.00638 |
| Sonnet 5.5 | $0.00319 | $0.00319 |
| Haiku 4.5 | $0.00160 | $0.00160 |
Grade A, and why
donnfelker-plugin-marketplace AGENTS.md 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.
How it starts
The opening of the file, as written. The whole thing — 187 lines — stays where its author put it; the contents beside it link to each section on GitHub.
AGENTS.md
Guidelines for AI agents working in this repository.
Repository Overview
This repository contains Agent Skills for AI agents following the Agent Skills specification. It also serves as a Claude Code plugin marketplace via .claude-plugin/marketplace.json.
- Name: Plugin Marketplace
- GitHub: donnfelker/donnfelker-plugin-marketplace
- License: MIT
Repository Structure
plugins/
└── plugin-name/
├── .claude-plugin/
│ └── plugin.json # Plugin manifest (name, description, version)
└── skills/
└── skill-name/
├── SKILL.md # Required skill file
├── references/ # Optional - detailed docs loaded on demand
├── scripts/ # Optional - executable code
└── assets/ # Optional - templates, data files
Build / Lint / Test Commands
Skills are content-only (no build step). Verify manually:
- YAML frontmatter is valid
namefield matches directory name exactlynameis 1-64 chars, lowercase alphanumeric and hyphens onlydescriptionis 1-1024 characters
Agent Skills Specification
Skills follow the Agent Skills spec.
Required Frontmatter
---
name: skill-name
description: What this skill does and when to use it. Include trigger phrases.
---
Frontmatter Field Constraints
| Field | Required | Constraints |
|---|---|---|
name |
Yes | 1-64 chars, lowercase a-z, numbers, hyphens. Must match dir. |
description |
Yes | 1-1024 chars. Describe what it does and when to use it. |
license |
No | License name (default: MIT) |
metadata |
No | Key-value pairs (author, version, etc.) |
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.
- 2mo ago First seen · 187 lines · 1,596 tokens per session scan A 39351adbab54
donnfelker-plugin-marketplace AGENTS.md is an instructions file published in the GitHub repository donnfelker/donnfelker-plugin-marketplace (4 stars, last pushed 4mo ago), licensed MIT. It adds 1,596 tokens to every session, about $0.0064 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 2026-08-31.
donnfelker-plugin-marketplace AGENTS.md compared with instructions from other repositories
| Mod | Type | Stars | Last push | Licence | Scan | Tokens | Works with |
|---|---|---|---|---|---|---|---|
| donnfelker-plugin-marketplace AGENTS.mddonnfelker/donnfelker-plugin-marketplace | Instructions file | 4 | 4mo ago | MIT | A | 1,596 | Claude Code, Codex, OpenCode |
| vscode buildNext.instructions.mdmicrosoft/vscode | Instructions file | 195k | today | MIT | A | 9,719 | GitHub Copilot |
| vscode oss-third-party-notices.instructions.mdmicrosoft/vscode | Instructions file | 195k | today | MIT | A | 5,516 | GitHub Copilot |
| next.js AGENTS.mdvercel/next.js | Instructions file | 143k | yesterday | MIT | A | 7,461 | Codex, OpenCode |
| langchain AGENTS.mdlangchain-ai/langchain | Instructions file | 149k | today | MIT | A | 4,680 | Codex, OpenCode |
| vscode copilot-instructions.mdmicrosoft/vscode | Instructions file | 195k | today | MIT | A | 3,093 | GitHub Copilot |
| vscode model-prompts.instructions.mdmicrosoft/vscode | Instructions file | 195k | today | MIT | A | 2,022 | GitHub Copilot |