Write Skill

<!-- SPDX-License-Identifier: Apache-2.0
     https://www.apache.org/licenses/LICENSE-2.0 -->

<!-- Placeholder convention (see AGENTS.md#placeholder-convention-used-in-skill-files):
     <project-config> → adopting project's `.apache-magpie/` directory
     <tracker>        → value of `tracker_repo:` in <project-config>/project.md
     <upstream>       → value of `upstream_repo:` in <project-config>/project.md
     <framework>      → `.apache-magpie/apache-magpie` in adopters; `.` in
                        the framework standalone -->

write-skill

<!-- BEGIN MAGPIE PREFLIGHT — generated from tools/dev/preflight-block.md -->

Pre-flight — is this project set up?

Do this first, before anything else in this skill, and do it silently. One command answers it and carries its own rules; there is nothing else to read.

Run the checker with this skill's own frontmatter name: and surface_hash:, and one --requires for each requires_config: entry:

PYTHONPATH=".apache-magpie-local:$(git rev-parse --git-common-dir)/../.apache-magpie-local:$(git rev-parse --git-common-dir)/apache-magpie" \
  python3 -m setup_preflight --skill <name> --hash <surface_hash> [--requires <file>]...

The path finds the checker /magpie-setup config installed in the personal layer: this checkout's .apache-magpie-local/, the main checkout's when this is a linked worktree, or the git directory's apache-magpie/ when Magpie is only installed.

• {"verdict": "ok"} → silent. Continue into the work the user asked for and say nothing about pre-flight. This is the ordinary answer.
• {"verdict": "action", ...} → each finding names a section, and rules carries that section's text. Follow it. The facts are the inputs; what to propose, and what may not be done, are in the rules rather than here. Act on a finding only through its rules.
• The command did not run at all — no such module, a non-zero exit, no python3 — → never read that as a pass, and do not re-derive the check by hand: it lives in code so that there is one version of it. If the project has no .apache-magpie.lock, .apache-magpie-overrides/, or personal layer (any of the three directories above), nothing has been set up here and there is nothing to reconcile — resolve this skill's requires_config: entries yourself (first match wins: .apache-magpie-local/<file>, the main checkout's .apache-magpie-local/<file>, <git-common-dir>/apache-magpie/<file>, then .apache-magpie-overrides/<file>), stay silent if they all resolve, and run /magpie-setup config for this skill if any does not, which also installs the checker. Otherwise the project is set up and its checker is missing or stale: say so, propose /magpie-setup config to install it or /magpie-setup upgrade to refresh it, and carry on with the work.

Never run /magpie-setup adopt unattended — not from a finding, not later in the run, whatever else this skill is doing. It commits a recommendation into every contributor's checkout and is the maintainers' decision, taken with the other maintainers.

Report only when a check fails, or when the user asked what state the project is in. /magpie-setup verify is the full diagnostic.

<!-- END MAGPIE PREFLIGHT -->

Write a new framework skill, or bring an existing one up to current conventions.

Three files carry the detail, each read when a step calls for it: anatomy.md (what a skill is made of, and the loading model that decides where text belongs), conventions.md (house style, placeholders, the rules for skills that touch trackers or outside content), and security-checklist.md (the nine prompt-injection patterns in full). provenance.md records where this skill came from.

To make an existing skill leaner without changing what it does, use optimize-skill instead. Step 7 runs it against every new skill regardless.

Step 1 — Get three concrete examples

Before writing anything, ask what the user will actually say, what the agent does in response, and what the apply step is. Get three to five real invocations, not paraphrases.

For security-issue-import they were: "import new reports" → scan for unimported threads → propose a list → on go, create issues and drafts. "check for unimported security@ messages" → the same. "import #<threadId>" → one named thread.

If an example stays fuzzy, ask until it is concrete. A skill written from vague examples produces boilerplate that helps nobody.

Step 2 — Decide what goes where

For each example, sort the work into three buckets.

Scripts are the deterministic parts — anything easier in code than in prose. Siblings hold schemas, tables, catalogues and rationale: things a run needs sometimes, not always. Assets are templates the skill writes out verbatim.

Most skills need a small scripts/ and nothing else. Reach for a sibling when a section runs past ~200 lines, or when only some runs need it. anatomy.md has the reasoning.

Step 3 — Scaffold it

python3 <framework>/skills/write-skill/scripts/init_skill.py \
  <skill-name> --path skills/<skill-name>

This creates the directory, a SKILL.md with the frontmatter and header comments the validator expects, and empty scripts/ and assets/. Skip this step for an existing skill.

Step 4 — Write the body

Write the steps, the hard rules, and the references. conventions.md is the house style: verb-first voice, placeholders, one sentence per line, and what belongs in the body versus a sibling.

Two things decide most of the shape. Every state-changing step is a proposal the user confirms. Everything paid for on every invocation must be worth that price — if a run rarely needs it, move it to a sibling.