Design Doc Creator

Design Doc Creator

Create well-structured design documents for features following project conventions.

Configuration

Environment Variable	Default	Description
DESIGN_DOCS_DIR	design_docs	Root directory for design documents
CHANGELOG_PATH	CHANGELOG.md	Path to changelog file
VERSION_FILE	VERSION	Path to version file (for auto-detecting current version)

Quick Start

Most common usage:

# User says: "Create a design doc for better error messages"
# This skill will:
# 1. Search for related existing design docs
# 2. Create ${DESIGN_DOCS_DIR:-design_docs}/planned/better-error-messages.md
# 3. Fill template with proper structure

When to Use This Skill

Invoke this skill when:

• User asks to "create a design doc" or "write a design doc"
• User says "plan a feature" or "design a feature"
• User mentions "document the design" or "create a spec"
• Before starting implementation of a new feature
• After completing a feature (to move to implemented/)

Available Scripts

scripts/create_planned_doc.sh <doc-name> [version]

Create a new design document in ${DESIGN_DOCS_DIR}/planned/.

Usage:

# Create doc in planned/ root (no version)
scripts/create_planned_doc.sh m-dx2-better-errors

# Create doc in next version folder
scripts/create_planned_doc.sh reflection-system v1_2_0

What it does:

• Detects current version from VERSION file or CHANGELOG
• Creates design doc from template
• Places in correct directory
• Fills in creation date

scripts/move_to_implemented.sh <doc-name> <version>

Move a design document from planned/ to implemented/ after completion.

Usage:

scripts/move_to_implemented.sh m-dx1-developer-experience v1_0_0

Workflow

Creating a Planned Design Doc

1. Gather Requirements

Ask user:

• What feature are you designing?
• What version is this targeted for?
• What priority? (P0/P1/P2)
• Estimated effort?
• Any dependencies on other features?

CRITICAL: Audit for Systemic Issues FIRST

Before writing a design doc for a bug fix, ALWAYS ask: "Is this part of a larger pattern?"

The Anti-Pattern (incremental special-casing):

v1: Add feature for case A
v2: Bug! Add special case for B
v3: Bug! Add special case for C
...forever patching

The Pattern to Follow (unified solutions):

v1: Bug report for case B
    BEFORE writing design doc:
    1. Search for similar code paths
    2. Check if A, C, D have same gap
    3. Design ONE fix covering ALL cases
v2: Unified fix - no future bugs in this area

Analysis Checklist (do BEFORE writing design doc):

• Is this a one-off or part of a pattern?
• Search codebase for similar code paths
• Check if other types/cases have the same gap
• Look at git history - has this area been patched repeatedly?
• Design fix to cover ALL cases, not just the reported one

Warning Signs of Fragmented Design:

• Multiple maps tracking similar things
• Switch statements with growing case lists
• Functions named handleX, handleY, handleZ instead of unified handle
• Bug fixes that add || specialCase conditions

2. Choose Document Name

Naming conventions:

• Use lowercase with hyphens: feature-name.md
• For milestone features: m-XXX-feature-name.md
• Be specific and descriptive
• Avoid generic names like improvements.md

3. Run Create Script

# If version is known
scripts/create_planned_doc.sh feature-name v1_2_0

# If version not decided yet
scripts/create_planned_doc.sh feature-name

4. Customize the Template

Fill in all sections: header metadata, problem statement, goals, solution design, examples, success criteria, testing strategy, timeline, risks.

5. Review and Commit

git add ${DESIGN_DOCS_DIR:-design_docs}/planned/feature-name.md
git commit -m "Add design doc for feature-name"

Moving to Implemented

When to move:

• Feature is complete and shipped
• Tests are passing
• Documentation is updated

scripts/move_to_implemented.sh feature-name v1_0_0

Design Doc Structure

See resources/design_doc_structure.md for:

• Complete template breakdown
• Section-by-section guide
• Best practices for each section
• Common mistakes to avoid

Best Practices

1. Be Specific

Use metrics, not vague statements. "Reduce build time from 7.5h to 2.5h (-67%)" not "Make development easier."

2. Include Metrics

Quantify current state and target improvements with real numbers.

3. Break Into Phases

Use checkboxes, estimated hours, and clear definitions of done.

4. Link to Examples

Reference real code, existing implementations, and prior art.

5. Realistic Estimates

2x your initial estimate. Include buffer for testing and documentation.

Document Locations

${DESIGN_DOCS_DIR:-design_docs}/
├── planned/              # Future features
│   ├── feature.md        # Unversioned (version TBD)
│   └── v1_2_0/           # Targeted for v1.2.0
│       └── feature.md
└── implemented/          # Completed features
    ├── v1_0_0/           # Shipped in v1.0.0
    │   └── feature.md
    └── v1_1_0/           # Shipped in v1.1.0
        └── feature.md

Version folder naming:

• Use underscores: v1_0_0 not v1.0.0
• Match CHANGELOG tags exactly
• Create folder when first doc needs it

Progressive Disclosure

This skill loads information progressively:

1. Always loaded: This SKILL.md file (workflow overview)
2. Execute as needed: Scripts create/move docs
3. Load on demand: resources/design_doc_structure.md (detailed guide)

Notes

• All design docs should follow the template structure
• Update CHANGELOG when features ship (separate from design doc)
• Keep design docs focused - split large features into multiple docs
• Use M-XXX naming for milestone/major features