Skill to SDK

Convert an Anthropic Agent Skill into a self-contained Python program that loads the skill's instructions as a system prompt and runs them against the Claude API. The output is a small command-line app the user runs with python app.py "their question" (or interactively) that prints the answer to the console.

Why this exists

A skill normally lives inside Claude Code / Claude.ai and triggers when its description matches. People often want to take a finished skill and run it as an ordinary program — to share it, schedule it, embed it, or call it from other code. This skill produces that program. The skill's instruction body becomes the system prompt; the user's question becomes the user message; the model's reply is printed to the console.

The wrapper is deliberately simple: one API call per turn, text in and text out, no tools. That is exactly what an instruction-only skill needs — a skill that just tells the model how to think, reason, format, or respond reproduces faithfully this way (e.g. market-sizing, okr-writer, exec-summary).

Input: two cases

The user will either hand you a SKILL.md or just describe a skill. Detect which and proceed accordingly.

1. They provide a SKILL.md (a file, a path, or pasted text): use it directly. Strip the YAML frontmatter — only the markdown body becomes the system prompt. Keep the name from the frontmatter to name the output folder and files.

2. They only give a name or description (e.g. "a skill that summarizes legal contracts"): first write a short, well-formed SKILL.md for it yourself — frontmatter with name and description, then a clear instruction body in the imperative voice describing how the assistant should behave. Show it to the user briefly, then wrap it. Keep it focused; a single-purpose instruction set is better than a sprawling one.

If anything essential is ambiguous (what the skill should actually do, what its name is), ask one concise question before generating. Otherwise proceed.

What to generate

Create a folder named after the skill (kebab-case, from the skill's name), containing exactly these files. Use the templates in assets/ as the starting point and fill in the skill-specific pieces.

<skill-name>-sdk/
├── skill/
│   └── SKILL.md          # the source skill (provided or generated)
├── app.py                # CLI: loads SKILL.md, calls the API, prints the reply
├── requirements.txt      # anthropic, python-dotenv
├── .env.example          # ANTHROPIC_API_KEY placeholder
└── README.md             # setup + run instructions, tailored to this skill

Copy assets/app_template.py to app.py verbatim — all the skill-specific content lives in skill/SKILL.md, so the runner itself never needs to change. Copy assets/requirements.txt and assets/.env.example as-is. Only edit app.py if the user explicitly asks for behavior the template doesn't cover (a different model, JSON output, or streaming).

What app.py does

The template runner:

• Loads skill/SKILL.md, strips the frontmatter (everything up to the second ---), and uses the remaining body as the system prompt.
• Handles input in three modes, in this order: (1) a command-line argument (python app.py "question") runs one-shot; (2) if there's no argument but input is piped in and there's no interactive terminal (sys.stdin.isatty() is false), it reads all of stdin as a single question — this is what makes echo "..." | python app.py and CI/non-interactive shells work; (3) only when a real terminal is attached, it drops into an interactive loop that keeps conversation history. This ordering matters: never enter the input() loop without a TTY, or it exits immediately and no conversation happens. When there's no argument, no TTY, and no piped input, it prints clear usage rather than silently doing nothing.
• Calls client.messages.create with model="claude-sonnet-4-6", max_tokens=2000, the system prompt, and the message history.
• Extracts the text blocks from the response and prints them to the console.
• Fails clearly if ANTHROPIC_API_KEY is missing, pointing the user to .env.example.

README.md

Base it on assets/README_template.md, then customize the title and the one-line description to match the specific skill, and add 2-3 realistic example invocations relevant to what this skill does. Keep the "Notes & limits" section — it sets correct expectations about what a text-only wrapper can do.

Scope: instruction-only skills

This wrapper is a plain text-in / text-out API call. It cannot run bundled scripts, read local files, or execute bash — so it reproduces instruction-only skills, the ones that just guide how the model thinks, reasons, formats, or responds. That covers the large majority of skills.

If the source skill genuinely needs to act — write files, read files, or run shell commands as part of its core job — say so plainly. The text-only wrapper will reproduce the skill's reasoning and describe the actions, but it won't perform them; making those real would require adding tool use (function calling) to app.py, which is out of scope here. Never silently imply a file-producing skill will write files when it won't.

Steps

1. Determine the input case (provided SKILL.md vs. name/description). If the latter, draft the SKILL.md and show it.
2. Note for the user whether the skill is fully instruction-only (reproduces faithfully) or relies on actions the text-only wrapper can't perform.
3. Create the folder structure from the assets/ templates.
4. Write the source skill into skill/SKILL.md.
5. Tailor README.md (title, description, examples) to this skill.
6. If a file-creation/output mechanism is available, save everything to the outputs location, zip it, and present it for download. Otherwise show the files inline.
7. Give the user the run instructions: create and activate a virtual environment (python -m venv .venv then source .venv/bin/activate, or .venv\Scripts\activate on Windows), install deps, copy .env.example to .env and add their key, then python app.py "a question".

Quick sanity check before delivering

• Frontmatter stripping works (the system prompt should not start with ---).
• The folder name and the skill name agree.
• requirements.txt lists anthropic and python-dotenv.
• The README's examples actually match what the skill does.
• You told the user whether the skill is fully instruction-only.