Borrowing it
Nothing to install: this file belongs to plainlang/plain-forge. 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/plainlang/plain-forge/main/.agents/skills/skill-creator/SKILL.mdgit clone --depth 1 https://github.com/plainlang/plain-forgeWrote 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/plainlang/plain-forge/skill-creator)<a href="https://agentmods.dev/skills/plainlang/plain-forge/skill-creator"><img src="https://agentmods.dev/badge/skills/plainlang/plain-forge/skill-creator/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/plainlang/plain-forge/skill-creator"><img src="https://agentmods.dev/badge/skills/plainlang/plain-forge/skill-creator.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 | $0.00052 | $0.00666 |
| Opus 5.5 | $0.00021 | $0.00266 |
| Sonnet 5.5 | $0.00010 | $0.00133 |
| Haiku 4.5 | $0.00005 | $0.00067 |
Grade A, and why
skill-creator 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 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.
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.
This is a copy
97% identical to skill-best-practices — 3 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 46 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Skill Authoring Procedure
Follow these steps to generate a skill that adheres to the agentskills.io specification and progressive disclosure principles.
Step 1: Initialize and Validate Metadata
- Define a unique
name: 1-64 characters, lowercase, numbers, and single hyphens only. - Draft a
description: Max 1,024 characters, written in the third person, including negative triggers. - Execute Validation Script: Run the validation script to ensure compliance before proceeding:
python3 scripts/validate-metadata.py --name "[name]" --description "[description]" - If the script returns an error, self-correct the metadata based on the
stderroutput and re-run until successful.
Step 2: Structure the Directory
- Create the root directory using the validated
name. - Initialize the following subdirectories:
scripts/: For tiny CLI tools and deterministic logic.references/: For flat (one-level deep) context like schemas or API docs.assets/: For output templates, JSON schemas, or static files.
- Ensure no human-centric files (README.md, INSTALLATION.md) are created.
Step 3: Draft Core Logic (SKILL.md)
- Use the template in
assets/skill-template.mdas the starting point. - Write all instructions in the third-person imperative (e.g., "Extract the text," "Run the build").
- Enforce Progressive Disclosure:
- Keep the main logic under 500 lines.
- If a procedure requires a large schema or complex rule set, move it to
references/. - Command the agent to read the specific file only when needed: "Read references/api-spec.md to identify the correct endpoint."
Step 4: Identify and Bundle Scripts
- Identify "fragile" tasks (regex, complex parsing, or repetitive boilerplate).
- Outline a single-purpose script for the
scripts/directory. - Ensure the script uses standard output (stdout/stderr) to communicate success or failure to the agent.
Step 5: Final Logic Validation
- Review the
SKILL.mdfor "hallucination gaps" (points where the agent is forced to guess). - Verify all file paths are relative and use forward slashes (
/). - Cross-reference the final output against
references/checklist.md.
What ships with it
3 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 · 46 lines · 52 tokens per session scan A 4f4e1529d1eb
skill-creator is a skill published in the GitHub repository plainlang/plain-forge (79 stars, last pushed yesterday), licensed MIT. It adds 52 tokens to every session and 666 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 97% identical to skill-best-practices, differing in 3 lines, and is treated as a copy.
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