Technical Spec Writer（技術仕様書作成）

Overview

This skill bridges the gap between requirements definition (BRD/User Stories) and implementation by producing structured, standards-compliant technical specification documents. It generates screen designs, API specifications, database designs, sequence diagrams, and state transition diagrams using Mermaid notation, following IEEE 830 and ISO/IEC/IEEE 29148 standards.

When to Use

• 要件定義（BRD）から技術仕様書を作成する
• 画面設計書を作成する
• API設計書を作成する
• DB設計書を作成する
• シーケンス図や状態遷移図を作成する
• 既存仕様書のレビューや改善を行う
• 要件からトレーサビリティマトリクスを作成する

Workflows

Workflow 1: Requirements Intake（要件取り込み）

Purpose: Gather and structure input requirements to determine document scope.

1. Receive input — Accept BRD, user stories, verbal requirements, or existing partial specs
2. Determine document scope — Classify the requested output:
   • 全体仕様書（Full functional specification）
   • 画面設計書（Screen design specification）
   • API設計書（API design specification）
   • DB設計書（Database design specification）
   • 個別ダイアグラム（Individual diagram）
3. Create document outline — Establish the ID numbering scheme:
   • SCR-xxx for screens
   • API-xxx for endpoints
   • TBL-xxx for tables
   • SEQ-xxx for sequence diagrams
   • STS-xxx for state diagrams
4. Establish traceability — Build a REQ-xxx to SCR/API/TBL mapping table to ensure every requirement is addressed
5. Confirm scope with user — Present the outline and confirm before proceeding
6. Load references/spec_writing_standards.md for ID conventions and quality criteria

Workflow 2: Screen Design Specification（画面設計）

Purpose: Produce detailed screen design documents with UI elements, events, and transitions.

1. Assign SCR-IDs — Number each screen sequentially (SCR-001, SCR-002, ...)

2. Define UI elements table for each screen:

   Element ID	Type	Label	Validation Rules	Default Value	Notes
   SCR-001-E01	text	User Name	Required, max 50 chars	—	—

3. Define event table for each screen:

   Event ID	Trigger Element	Event Type	Action	Target
   SCR-001-EV01	btn_submit	click	POST /api/v1/users	SCR-002

4. Create screen transition diagram — Use Mermaid stateDiagram-v2 to visualize navigation flow

5. Add responsive breakpoint notes — Document layout changes at standard breakpoints (mobile 375px, tablet 768px, desktop 1024px+)

6. Reference references/mermaid_diagram_patterns.md for diagram syntax

7. Output using assets/functional_spec_template_ja.md or assets/functional_spec_template_en.md

Workflow 3: API Design Specification（API設計）

Purpose: Produce REST API specifications with endpoints, schemas, and sequence diagrams.

1. Assign API-IDs — Number each endpoint sequentially (API-001, API-002, ...)
2. Define each endpoint:
   • HTTP Method and Path
   • Description and authentication requirements
   • Request parameters, headers, and body (JSON schema)
   • Response body (success and error)
   • Error codes with business error code mapping
3. Provide request/response JSON examples — Include realistic sample data
4. Standardize error codes — Use the error envelope pattern from references/api_design_guide.md
5. Create sequence diagrams — For multi-service or complex flows, produce Mermaid sequenceDiagram
6. Load references/api_design_guide.md for REST conventions
7. Output using assets/api_spec_template.md for per-endpoint detail

Workflow 4: Database Design Specification（DB設計）

Purpose: Produce database design documents with table definitions, ER diagrams, and indexes.

1. Assign TBL-IDs — Number each table sequentially (TBL-001, TBL-002, ...)

2. Define column definition table for each table:

   Column Name	Data Type	Nullable	Default	Description	Constraints
   id	BIGINT	NO	AUTO_INCREMENT	Primary key	PK

3. Create ER diagram — Use Mermaid erDiagram to visualize relationships

4. Define index table — Document all indexes with type, columns, and purpose

5. Include audit columns — Ensure every table has: created_at, updated_at, created_by, updated_by

6. Add soft delete support where appropriate — deleted_at column

7. Load references/db_design_guide.md for naming conventions and normalization guidance

8. Output using assets/db_design_template.md for per-table detail

Workflow 5: Sequence Diagram Creation（シーケンス図）

Purpose: Produce Mermaid sequence diagrams for system interaction flows.

1. Identify participants — Categorize actors:
   • Actor (user)
   • Frontend (browser/app)
   • Backend (API server)
   • Database
   • External API / Third-party services
2. Map message flow — Document request/response patterns for the target scenario
3. Add conditional branches — Use alt, opt, loop fragments as needed
4. Add notes and activations — Clarify processing steps and active lifelines
5. Output Mermaid sequenceDiagram code block
6. Reference references/mermaid_diagram_patterns.md for syntax patterns

Workflow 6: State Transition Diagram Creation（状態遷移図）

Purpose: Produce state machines for entities with lifecycle behavior.

1. Build state inventory table:

   State ID	Name	Description	Entry Condition	Exit Condition
   STS-001	Draft	Initial state	Record created	Submit action

2. Build transition table:

   From State	Event/Trigger	Guard Condition	Action	To State
   Draft	Submit	All required fields filled	Validate & save	Pending Review

3. Create state transition matrix — States as rows, events as columns, target state in cells

4. Output Mermaid stateDiagram-v2 code block

5. Reference references/mermaid_diagram_patterns.md for state diagram syntax

Workflow 7: Document Assembly（ドキュメント組み立て）

Purpose: Assemble individual sections into a complete specification document.

1. Generate table of contents — Auto-generate from section headers
2. Cross-reference validation — Verify all IDs are referenced correctly:
   • Every REQ-xxx maps to at least one SCR/API/TBL
   • Every SCR-xxx event references a valid API-xxx or screen target
   • Every API-xxx references valid TBL-xxx tables
3. Quality checklist — Verify the document meets IEEE 830 criteria:
   • Completeness — All requirements addressed
   • Consistency — No contradictions between sections
   • Traceability — Bidirectional mapping maintained
   • Unambiguity — No vague language ("appropriate", "etc.", "as needed")
   • Verifiability — Each requirement can be tested
   • Modifiability — Modular structure with clear cross-references
4. Select output template — Use the appropriate template from assets/:
   • Full spec: functional_spec_template_ja.md or functional_spec_template_en.md
   • API only: api_spec_template.md
   • DB only: db_design_template.md
5. Fill template placeholders — Replace all {PLACEHOLDER} values with actual content

Resources

File	Purpose	When to Load
references/spec_writing_standards.md	IEEE 830/ISO 29148 standards, ID conventions, quality criteria	Workflow 1 (Requirements Intake), Workflow 7 (Document Assembly)
references/mermaid_diagram_patterns.md	Mermaid syntax patterns for all diagram types	Workflow 2, 5, 6 (any diagram creation)
references/api_design_guide.md	REST design principles, error formats, pagination	Workflow 3 (API Design)
references/db_design_guide.md	Naming conventions, normalization, index strategy	Workflow 4 (DB Design)
assets/functional_spec_template_ja.md	Full functional spec template (Japanese)	Workflow 7 when output language is Japanese
assets/functional_spec_template_en.md	Full functional spec template (English)	Workflow 7 when output language is English
assets/api_spec_template.md	Per-endpoint API specification template	Workflow 3, 7 for API-focused output
assets/db_design_template.md	Per-table database design template	Workflow 4, 7 for DB-focused output

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Best Practices

Do's

• 各設計要素にIDを採番し、要件とのトレーサビリティを維持する
• 曖昧な用語（「適切な」「必要に応じて」「等」）を避け、SHALL/SHOULD/MAYで記述する
• 画面・API・DBの相互参照を検証してから出力する
• Mermaidダイアグラムは方向・命名規則を統一する
• テンプレートのプレースホルダーを一つ残らず置換する

Don'ts

• 要件の取りこぼしを放置しない（トレーサビリティマトリクスで確認）
• 1つの画面設計に複数の関心事を混在させない
• APIの正常系だけ記述してエラー系を省略しない
• インデックス戦略なしにテーブル定義だけ書かない

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Examples

例1: ECサイト商品管理画面の技術仕様書

User: 商品管理画面の技術仕様書を作成してください。
      要件: 商品CRUD、カテゴリ管理、画像アップロード、在庫管理

Claude:
1. [Workflow 1] 要件取り込み → SCR-001〜003、API-001〜008、TBL-001〜004 を採番
2. [Workflow 2] 画面設計 → 商品一覧(SCR-001)、商品登録/編集(SCR-002)、カテゴリ管理(SCR-003)
3. [Workflow 3] API設計 → GET/POST/PUT/DELETE /api/v1/products、POST /api/v1/images
4. [Workflow 4] DB設計 → products、categories、product_images、inventory テーブル + ER図
5. [Workflow 7] 組み立て → functional_spec_template_ja.md で出力

例2: API設計書のみ作成

User: 認証APIの設計書だけ作ってください。JWT認証です。

Claude:
1. [Workflow 1] スコープ: API設計のみ → API-001〜003（login, refresh, logout）
2. [Workflow 3] 各エンドポイントの詳細設計（リクエスト/レスポンス/エラー）
3. [Workflow 5] 認証フローのシーケンス図（Client → API → DB → JWT発行）
4. [Workflow 7] api_spec_template.md で出力