pie-prd-author

name	pie-prd-author
description	Drafts or updates a PIE element PRD following the project conventions in docs/prds/README.md. Use when starting a new element that meets the PRD bar, or when a substantial change requires updating an existing PRD.
allowed-tools	Read, Write, Edit, Glob, Grep

PIE PRD Author

Drafts or updates a PRD for a new element or substantial feature change.

When a PRD Is Required

From AGENTS.md (verbatim):

• New elements (net-new @pie-element/* packages or substantial new interaction types).
• Non-trivial extensions of existing elements (anything that adds an authoring-visible config, a new mode, or a materially new delivery surface).
• Cross-cutting platform changes that touch model / session / event contracts across multiple elements (e.g. shared-stimulus container, parameterized items, event consistency work).
• Authoring-surface changes that shift how authors compose item content.

Does not require a PRD: bug fixes, refactors with no behaviour change, demo tweaks, docs / README changes, version bumps, dependency updates, or retroactive documentation of stable elements you are not actively changing.

Retroactive PRDs for existing elements: do not write them preemptively. Tests own behaviour; a PRD written after the fact drifts from the code and creates a second source of truth with no active reader. Exception: write a thin PRD for an existing element when you are about to touch it — capture only intent not derivable from the code (key non-goals, deliberate upstream divergences). One screen is enough.

Process

1. Read docs/prds/_template.md — this is the copy-paste starter.
2. Read docs/prds/venn-classification/PRD.md — canonical length and tone. Target that density.
3. Read CONTEXT.md, docs/prds/README.md, the relevant existing PRD if one exists, and nearby element examples. Use established repo terminology for model, session, mode, controller, and authoring concepts; do not invent synonyms.
4. Identify the slug: element name or feature name in kebab-case. It becomes docs/prds/<slug>/PRD.md.
5. Check whether a PRD already exists at that path before creating a new one.
6. Draft into docs/prds/<slug>/PRD.md. Cover: Context, Goals, Non-goals, Proposed surface (Model, Session, Modes, Controller responsibilities, Authoring surface), Worked example, Accessibility, Open questions.
7. Present the draft inline in the conversation and ask the user to confirm the status and content before writing to disk.

What to Cover

Model: list only the key fields with a one-line description each. No TypeScript interfaces — those live in code. 4–6 fields is the right depth.

Session: same discipline. At minimum cover the response shape and completed.

Modes: list which modes the element must handle (gather, view, evaluate, configure) and what each does.

Controller responsibilities: validate() rules (what it rejects and why), outcome() scoring policy, createCorrectResponseSession() invariant.

Authoring surface: what the author sees and can configure. Keep it behavioural, not visual-design-prescriptive.

Worked example: one concrete scenario — a real prompt, real tiles/choices, a submitted session as JSON, and the resulting score. This is the most valuable section for constraining implementation.

Accessibility: keyboard model, screen-reader annoucements, hit-target sizes, color-independence requirements. Be specific to this element's interaction type.

Open questions: only genuinely undecided items. When resolved, delete the bullet and inline the answer into the relevant section.

Length Discipline

Target: one screen (~60 lines of markdown). Red flags that indicate over-expansion:

• Full TypeScript interface definitions in the PRD body.
• Generic "Performance", "Security", or "Observability" sections with no element-specific content — omit them entirely.
• A dated "Decision log" section — inline rationale next to the Non-goal or field it applies to.
• Owner / date fields — git tracks these; do not add them.
• A "Resolved questions" section — resolved items are deleted and inlined.

Non-Goals Discipline

Every Non-goal that a reader might push back on must include a one-sentence inline reason. This is the section agents misread most often.

Example pattern:

- **No per-tile scoring weights.** All tiles score equally; weights add authoring complexity
  with marginal pedagogical benefit for K-8 formative use.

Without the reason, an agent implementing the element may silently add weights because they seem obviously useful.

Status Rules

• New PRDs start as Proposal.
• Transition to Accepted only when the implementation contract is agreed (explicitly confirmed by the maintainer in conversation or PR review).
• Never add a Shipped status — tests and release tags own that information.
• The optional ## Status log section records transitions only (Proposal → Accepted), not content edits. A fresh Proposal with no transitions does not need this section.

Facet Splitting Rule

The default is a single PRD.md covering all facets. Only split into delivery.md / authoring.md / print.md when a facet has outgrown approximately two screens of element-specific content. Model / Session / event shape always stays in PRD.md — never duplicate it into a facet file.

Tool Usage

• Read: CONTEXT.md, docs/prds/README.md, docs/prds/_template.md, docs/prds/venn-classification/PRD.md, any existing PRD at the target path, and nearby element examples when terminology is unclear.
• Glob: find existing PRDs (docs/prds/**/PRD.md) to check for prior art or a related element's surface.
• Grep: scan for terminology conflicts or existing usage of a proposed field name.
• Write / Edit: only after the user confirms the draft in conversation.