Writing Feature Specs

Guides the creation of comprehensive feature specification documents through structured research and user interviews.

Workflow

1. Gather Requirements

Ask the user:

• What is the feature we are building?
• What problem are we solving?
• Who asked for this / user feedback if any?
• Any constraints: timeline, dependencies, etc.?
• What is the local path for the backend, frontend and documentation?

2. Clarify the Data Model

Before assuming domain terms, clarify:

• What entities exist and how do they relate?
• Are there similar-sounding concepts that are actually distinct? (e.g., User vs Membership, Account vs Organization)
• Ask the user to confirm your understanding before proceeding

3. Research (do in parallel)

Before writing the spec, research:

1. Explore existing system - Search the codebase to understand current architecture
2. External API/integration docs - Read official docs if applicable
3. Similar features - Find prior art for consistency and patterns

Search these directories for relevant information:

• Backend source code in the local path from earlier
• Frontend source code in the local path from earlier
• Documentation directories in the local path from earlier
• Any other related files or directories from earlier

4. Write the Spec

Use the template at templates/spec.md in this skill directory.

Output the spec to the project's specs directory (e.g., .specs/[FEATURE-NAME].md or specs/[FEATURE-NAME].md).

Code References

For references to code files, use GitHub URLs (not local file:// URLs):

• Get the repo URL from git remote get-url origin
• Use format: https://github.com/{org}/{repo}/blob/{branch}/{path}#L{line}-L{line}

Minimize Implementation Details

• Describe the contract (what), not the implementation (how)
• Use JSON schema for data models, not internal formats like protobuf
• Omit infrastructure choices (databases, queues, frameworks) unless they constrain the design
• If an implementation detail is necessary, explain why it matters to the reader

Design Principles

Always remember:

• Start from user goals and tasks, not screens
• Design the smallest useful version that can be shipped
• Avoid implying future functionality that is not committed

Frontend Design Rules

Apply these rules ONLY for frontend/UI features:

Hierarchy & Structure:

• Treat hierarchy as the primary UX tool - decide what matters most on every screen
• Use constraints to reduce complexity and decision fatigue
• Separate semantic correctness from visual importance
• Prefer clarity and scannability over completeness

User Actions:

• Explicitly identify primary, secondary, and tertiary user actions
• Describe what information users must notice first and why
• Do not assume the user will understand the feature

Iteration:

• Assume designs will be iterated after real usage
• Recommend when to defer design decisions until implementation feedback exists
• Call out assumptions, risks, and unknowns instead of masking them with UI
• Optimize for learnability and reduction of cognitive load