# 0018 — factory/write-skill (bootstrap skill)

**Type:** HITL  
**Parent PRD:** `docs/prd/chunk-3-skills-library.md`

## What to build

### Phase 1: `write-skill`

Build `write-skill` — the second bootstrap skill. Once complete, it is used to author all subsequent SKILL.md files in Chunk 3.

**Trigger description** (from skills index): "Write a new skill for X, create a SKILL.md that does Y"

**Key constraints:**
- Produces a complete SKILL.md following the authoring standard in `docs/notes/skill-implementation-workflow.md`
- Validates trigger description against explicit, implicit, and negative test queries before completing
- Flags if the proposed skill overlaps with an existing skill in the library
- Skill file: `.agents/skills/write-skill/SKILL.md`; `metadata.category: factory`
- SKILL.md is hand-written (write-skill cannot author itself before it exists)
- Eval via `write-eval` (issue 0017)

### Phase 2: `write-docs`

Build `write-docs` — the first skill authored via `write-skill` itself (the factory eating itself for the first time). Implement immediately after phase 1 is complete and deployed.

**Trigger description** (from skills index): "Write documentation for X, document this module, create docs for this feature"

**Key constraints:**
- Skill file: `.agents/skills/write-docs/SKILL.md`; `metadata.category: implement`
- SKILL.md authored via `write-skill`; eval via `write-eval`
- Follow full per-skill workflow from `docs/notes/skill-implementation-workflow.md` (sub-agents for discovery, review, conflict check)
- Derives from code and spec; never invents behaviour

## Implementation notes

Follow the per-skill workflow defined in `docs/notes/skill-implementation-workflow.md` (produced by issue 0016).

**Known upstream sources to review:**
- `mattpocock/skills` — contains `write-a-skill`, the direct Pocock equivalent; review at current HEAD; record SHA in `source:` for any adopted content
- agentskills.io open standard — the SKILL.md format spec is the authoritative reference for what `write-skill` must produce; cross-reference against the standard before finalising output format constraints
- `bmad-method/bmad-method` — check for any skill-authoring or template-writing patterns

## Acceptance criteria

- [ ] `.agents/skills/write-skill/SKILL.md` exists; `metadata.category: factory`; authoring standard met
- [ ] Trigger description validates against explicit, implicit, and negative test queries
- [ ] `.agents/evals/factory/write-skill/eval.yaml` exists; produced via `write-eval`
- [ ] `install.sh` deploys `write-skill` to `~/.agents/skills/`
- [ ] **HITL:** human runs behavioral test: invoke "write a new skill for X" and verify the produced SKILL.md meets the authoring standard
- [ ] **HITL:** human reviews SKILL.md and eval before committing
- [ ] Per-skill process followed for both phases (see `docs/notes/skill-implementation-workflow.md`)
- [ ] Trigger description for each skill tested against explicit, implicit, and negative queries before body written
- [ ] `when:` frontmatter field present in both SKILL.md files
- [ ] `source:` and `references:` fields correctly populated or absent
- [ ] eval.yaml for each skill contains all 5 required test types
- [ ] Body ≤500 lines for each skill
- [ ] Phase 2 (`write-docs`) is the first skill produced end-to-end by the factory
- [ ] `docs/spec/overview.md` updated to reflect both skills deployed

## Blocked by

- 0016 (grill defines per-skill workflow)
- 0017 (`write-eval` needed to produce the eval for this skill)