/phx-document

name: phx-document
description: 'Use when asked to document Elixir code: add or fill in @moduledoc and
  @doc for modules and functions. Documents tested code only; may add a README section
  or ADR. Not for docs lookup or audits.'

Document

Generate documentation for newly implemented features.

Usage

phx-document .claude/plans/magic-link-auth/plan.md
phx-document magic link authentication
phx-document  # Auto-detect from recent plan

Iron Laws

1. **Never remove existing documentation** — Existing docs may reflect design intent that isn't obvious from code alone; update rather than replace 2. **@moduledoc on every public module** — Undocumented modules accumulate quickly and create onboarding friction for new team members 3. **ADRs capture the "why", not the "what"** — Code shows what was built; ADRs explain why this approach was chosen over alternatives 4. **Match @doc to function's public API** — Document parameters, return values, and edge cases; callers shouldn't need to read the implementation 5. **DO NOT add @doc to untested code** — documentation implies a stable contract; document only after tests confirm the function behaves as described

What Gets Documented

| Output | Description | |--------|-------------| | `@moduledoc` | For new modules missing documentation | | `@doc` | For public functions without docs | | README section | For user-facing features | | ADR | For significant architectural decisions |

Workflow

Step 0: Pre-check (avoid no-op runs)

Run `git diff --name-only HEAD~5 | grep '\.ex$' | head -20` to check for new `.ex` files.

If no new `.ex` files were added (only modifications), skip the full audit and report: "No new modules — documentation coverage unchanged." A full audit of unchanged coverage produces nothing to add.

1. **Identify** new modules from recent commits or plan file 2. **Check** documentation coverage (`@moduledoc`, `@doc`) 3. **Generate** missing docs using templates 4. **Add** README section if user-facing feature 5. **Create** ADR if architectural decision was made 6. **Write** report to `.claude/plans/{slug}/reviews/{feature}-docs.md`

When to Generate ADRs

| Trigger | Create ADR | |---------|-----------| | New external dependency | Yes | | New database table | Maybe (if schema non-obvious) | | New OTP process | Yes (explain why process needed) | | New context | Maybe (if boundaries non-obvious) | | New auth mechanism | Yes | | Performance optimization | Yes |

Integration with Workflow

phx-plan → phx-work → phx-review
       ↓
phx-document  ← YOU ARE HERE (optional, suggested after review passes)

References

• `references/doc-templates.md` — @moduledoc, @doc, README, ADR templates
• `references/output-format.md` — Documentation report format
• `references/doc-best-practices.md` — Elixir documentation best practices
• `references/documentation-patterns.md` — Detailed documentation patterns