Feasibility Study Skill

Trigger

• Keywords: feasibility, is this possible, can we, should we, explore options, before tech spec

When NOT to Use

• Already have a tech spec (use /deep-analyze)
• Need implementation, not analysis (use /codex-implement)
• Quick question (use /codex-explain or /codex-architect)

Workflow

Decompose → Constraints → Code research → Solutions → Codex discussion → Decision → Report

Phase 1: Requirement Decomposition

Use "5 Why" to uncover essence:

1. Surface requirement (what user asks for)
2. Underlying problem (why they need it)
3. Success criteria (quantifiable acceptance)

Phase 2: Constraint Analysis

Inventory constraints by type (Technical, Business, Resource, Compatibility) with flexibility rating.

Phase 3: Code Research

Research existing codebase:

• Related modules and reusable logic
• Existing design patterns
• Tech debt to work around

Phase 4: Solution Exploration

Brainstorm 2-3+ solutions, each with:

1. Core idea (one sentence)
2. Implementation path
3. Quantified feasibility (see @references/analysis-phases.md)
4. Cost and trade-offs

Phase 5: In-Depth Codex Discussion

⚠️ Core step — not optional (unless --no-codex) ⚠️

See @references/codex-discussion-guide.md for full rules and examples.

Tool	Purpose	When
/codex-brainstorm	Enumerate all options	At start
/codex-architect	Evaluate design	After proposal forms
mcp__codex__codex-reply	Ask details	Anytime

Phase 6: Comparative Decision

Side-by-side comparison → recommendation + backup + open questions.

Evaluation Dimensions

Dimension	Green	Yellow	Red
Technical Feasibility	Has existing patterns	Needs adaptation	Major innovation
Effort	< 3 person-days	3-10 person-days	> 10 person-days
Risk	Small scope	Some uncertainty	Many unknowns
Extensibility	Easy to extend	Needs refactoring	Hard to extend
Maintenance Cost	Clean, easy	Some complexity	Complex

Output

## Feasibility Study: <title>
### Quantitative Comparison
| Criterion | Option A | Option B | Option C |
|-----------|----------|----------|----------|

### Recommendation
<selected option with rationale>

Verification

• 5 Why decomposition completed
• Constraints inventoried with flexibility
• Existing code researched (grep/read)
• 2-3+ solutions explored with quantified assessment
• Codex discussion documented (unless --no-codex)
• Comparison table + recommendation + open questions

References

• Analysis phases: references/analysis-phases.md
• Codex discussion: references/codex-discussion-guide.md
• Output template: references/output-template.md

Relationship with Other Commands

/feasibility-study → /tech-spec → /deep-analyze → /codex-implement

Examples

Input: /feasibility-study "Add user quota management"
Action: 5 Why → constraints → code research → 3 solutions → Codex discussion → recommendation

Input: /feasibility-study "Optimize cache" --context src/service/cache.ts
Action: Read cache code → constraints → solutions → Codex brainstorm → comparison → report