product-requirements-doc

Product Requirements Document

A PRD translates a vague or complex feature request into a structured artifact that complements task.md. The questioner produces it when intent is rich enough to need explicit scope, acceptance criteria, and constraints, rather than a one-page task summary alone.

The goal is precision, not exhaustive documentation: clear scope, unambiguous acceptance criteria, and explicit boundaries that prevent scope creep when the design-author later turns the task into an approach.

When to Write a PRD

The questioner produces a PRD (in addition to the standard task.md and questions.md) when the feature request is:

• Vague or underspecified — the request does not say what "done" looks like ("improve the onboarding experience" has no clear scope boundary)
• Complex with multiple user stories — more than one user type, more than one distinct workflow, or multiple independent but related capabilities
• Cross-cutting — the feature touches multiple subsystems and the interaction between them needs explicit specification
• Replacing or significantly changing existing behavior — where the scope of "existing" needs to be defined before research can begin

For simple, well-scoped requests ("add a --verbose flag to the CLI"), the standard task.md is sufficient — no PRD needed.

PRD Structure

Write the PRD to docs/plans/<id>/prd.md. Reference its path from task.md so the design-author knows to read it.

Problem Statement

One to three sentences: what problem does the user have? Why does it exist? Why does it matter to solve it now? Ground every subsequent section in this.

User Stories

Enumerate the user workflows the feature must support. Use this format:

As a [user type], I want to [action], so that [outcome].

Every user story that is in scope gets listed. User stories that are explicitly out of scope get listed in Non-Goals. Stories that might be in scope later get listed in Future Scope.

Keep stories at the "what" level, not the "how" level. "As a developer, I want to see syntax errors highlighted in the editor" is a story. "As a developer, I want the parser to return an AST node with error metadata" is an implementation detail.

Acceptance Criteria

For each user story, define the conditions that prove it is implemented correctly. Acceptance criteria are written as verifiable statements:

GIVEN [initial context]
WHEN [user action]
THEN [expected outcome]

Or as a checklist when the story is simple:

- [ ] The user can do X without doing Y first
- [ ] Doing X with invalid input shows error message Z
- [ ] Doing X is reflected in the audit log within 1 second

Acceptance criteria must be:

• Testable — can be verified by running a test or observing behavior
• Unambiguous — only one interpretation is possible
• Complete — cover happy path, error cases, and edge cases

Scope Boundaries

Explicit statement of what is and is not in scope.

In Scope:

• List every feature, behavior, or capability that must be delivered

Out of Scope:

• List everything that is explicitly excluded — even obvious things if they might be assumed. "Does not support X" is more valuable than silence.

Future Scope:

• Desirable features that are deliberately deferred. Capturing them here prevents them from being lost while keeping them out of the current scope.

Constraints

Non-negotiable requirements the implementation must satisfy:

• Performance: response time, throughput, latency budgets
• Compatibility: API versioning, backward compatibility, browser support
• Security: authentication, authorization, data handling requirements
• Operational: deployment constraints, infrastructure requirements

Consuming a PRD downstream

When the design-author finds a PRD path referenced in task.md, it should:

1. Read the PRD first. The PRD supersedes any ambiguity in the original feature request.
2. Map acceptance criteria to design decisions. Each criterion grounds one or more decisions in the design document.
3. Use the scope boundaries as the scope fence. Subsequent structure + plan must not add slices for out-of-scope items.

When the structure-planner reads the design, the PRD's acceptance criteria become the source of vertical-slice acceptance tests.

Rules

• PRDs describe behavior, not implementation. The PRD tells the design author what users need; the design tells the implementer how to build it.
• Every acceptance criterion must be testable. If you cannot write a test for it, it is not an acceptance criterion — it is an aspiration.
• Scope boundaries are commitments. Out-of-scope means out-of-scope for this feature, regardless of how easy it seems to add.
• The PRD belongs to the questioner. The design-author may surface questions about acceptance criteria interactively but may not change them unilaterally.