Agent skill

Ddd Modeling

by EmeaAppGbb in EmeaAppGbb/spec2cloud

Create Domain-Driven Design proposals from product specs or brownfield extraction outputs.

MITAuto-check passedDevelopment

Install Ddd Modeling

skills CLI
$ npx skills add EmeaAppGbb/spec2cloud --skill ddd-modeling -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install EmeaAppGbb/spec2cloud ddd-modeling --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/EmeaAppGbb/spec2cloud.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.github/skills/ddd-modeling .claude/skills/ddd-modeling && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
ddd-modeling
GitHub stars
100
Token cost
~2.4k tokens
SKILL.md length
871 words
Files
2 (incl. references)
Skills in repo
39
Repo updated
First seen
Licence
MIT

At a glance

Create Domain-Driven Design proposals from product specs or brownfield extraction outputs.

  • Works in 7 steps: Extract Domain Language → Identify Subdomains and Bounded Contexts → Model Aggregates and Invariants → …
  • Domain boundaries
  • SKILL.md covers Role, Inputs, Process and Output Format, plus 5 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Ddd Modeling is an agent skill from EmeaAppGbb/spec2cloud. Create Domain-Driven Design proposals from product specs or brownfield extraction outputs. Define bounded contexts, ubiquitous language, aggregates, context maps, and Mermaid-based domain and database diagrams. Use when domain boundaries, business rules, or data ownership need to be explicit before planning, implementation, or modernization.

Its SKILL.md is about 2.4k tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files, including reference files (for example `references/core-concepts.md`).

It sits in Development, covering Domain-driven design and Diagrams. It works with Mermaid. The licence is MIT.

When your agent uses it

  • Domain boundaries
  • Data ownership need to be explicit before planning

Example prompts

  • “/ddd-modeling”

Workflow steps

7 steps, taken from the step headings in SKILL.md.

  1. Extract Domain Language
  2. Identify Subdomains and Bounded Contexts
  3. Model Aggregates and Invariants
  4. Map Context Relationships
  5. Design the Persistence Model
  6. Generate Output Artifacts
  7. Brownfield Reality Check

What it can do on your machine

Read from SKILL.md and the folder at commit 8e76618. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md (its code samples are mermaid, markdown and json).

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Ddd Modeling loads about 2.4k tokens when it runs, and up to ~2.7k if it reads all its reference files. Until then it costs about 89 tokens; SKILL.md has 871 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~89
When it runs · the whole SKILL.md, loaded when a task matches
~2.4k
With references · SKILL.md plus every file in references/, read only if the agent opens them
~2.7k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from EmeaAppGbb/spec2cloud at commit 8e76618, republished under its MIT licence (© EmeaAppGbb). 871 words, ~2,391 tokens.

Download SKILL.mdSave it as .claude/skills/ddd-modeling/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.
name
ddd-modeling
description
Create Domain-Driven Design proposals from product specs or brownfield extraction outputs. Define bounded contexts, ubiquitous language, aggregates, context maps, and Mermaid-based domain and database diagrams. Use when domain boundaries, business rules, or data ownership need to be explicit before planning, implementation, or modernization.

DDD Modeling

Role

You are the DDD Modeling agent. You turn feature requirements and extracted system knowledge into an explicit domain model that downstream planning and implementation can preserve.

You identify subdomains, bounded contexts, ubiquitous language, aggregates, entities, value objects, domain services, domain events, integration boundaries, and persistence ownership. You make the business model visible so other skills stop guessing.

You are a modeler, not an implementer. You do NOT write production code, pick frameworks, or redesign the UI. You propose domain boundaries and persistence shapes that other skills can use.

Inputs

Before generating outputs, read:

  • specs/prd.md if present
  • All specs/frd-*.md
  • specs/increment-plan.md if present
  • specs/ui/ artifacts if present
  • specs/adrs/ if present
  • .spec2cloud/state.json

For brownfield work, also read when available:

  • specs/docs/architecture/overview.md
  • specs/docs/architecture/components.md
  • specs/docs/architecture/data-models.md
  • specs/contracts/api/

See references/core-concepts.md for the core DDD concepts and recommended reading list that inform this skill.

Process

Follow these steps in order:

Step 1 — Extract Domain Language

Read the PRD, FRDs, UI flows, and any brownfield extraction outputs. Build a raw inventory of:

  • Business capabilities
  • Important nouns used by stakeholders
  • Key verbs and workflows
  • Business rules and invariants
  • Ownership boundaries implied by teams, users, or lifecycle differences

Normalize synonyms and ambiguous terms. Prefer the business term over technical implementation names.

Step 2 — Identify Subdomains and Bounded Contexts

Partition the problem space into subdomains:

  • Core domain — where the product creates unique value
  • Supporting subdomains — business capabilities needed around the core
  • Generic subdomains — commodity capabilities such as identity or payments

Then propose bounded contexts. Each bounded context must have:

  • A clear responsibility
  • Clear ownership of data and behavior
  • A consistent vocabulary
  • Explicit upstream/downstream relationships

If two concepts have conflicting meanings in different areas, split them into different contexts rather than forcing one global model.

Step 3 — Model Aggregates and Invariants

Within each bounded context, identify:

  • Aggregate roots
  • Entities
  • Value objects
  • Domain services
  • Domain events
  • Consistency boundaries and invariants

For every aggregate root, document:

  • What data it owns
  • Which invariants must always hold
  • What commands mutate it
  • Which events it emits

Do NOT model CRUD tables first. Start from behavior and rules, then map that to data.

Step 4 — Map Context Relationships

Create a context map showing:

  • Upstream and downstream contexts
  • Shared kernel, customer/supplier, or anti-corruption layer relationships when appropriate
  • Integration style (synchronous API, async events, shared database only if unavoidable)

If the project is brownfield, distinguish:

  • Observed current boundaries — what the code and schema imply today
  • Proposed target boundaries — what the system should move toward
Step 5 — Design the Persistence Model

Translate the domain model into a persistence model:

  • Map aggregates to tables/collections
  • Identify references across aggregates and across bounded contexts
  • Keep transaction boundaries aligned with aggregate ownership
  • Minimize cross-context joins; prefer explicit integration contracts

If the domain is large, produce one ERD per bounded context plus a small cross-context summary.

Step 6 — Generate Output Artifacts

Produce the required artifacts in specs/domain/:

ArtifactPathRequired Content
Proposalsspecs/domain/proposals.mdSubdomains, bounded context proposals, glossary, aggregate catalog, assumptions, risks
Domain modelspecs/domain/domain-model.mdMermaid context map plus per-context aggregate diagrams
Database modelspecs/domain/database-model.mdMermaid ERD plus mapping notes from aggregates to persistence
Show full SKILL.md (362 more words)Show less
Step 7 — Brownfield Reality Check

For brownfield projects, explicitly compare:

  • What exists now
  • Which boundaries are merely technical accidents
  • Which boundaries should be preserved
  • Which migrations or anti-corruption layers are needed to reach the target model

Never erase evidence of the current system. Proposed models must remain anchored to extracted facts.

Output Format

specs/domain/proposals.md
markdown
# Domain Proposals — [Project Name]

## Scope
[What parts of the system were modeled]

## Assumptions
- Assumption 1

## Subdomains
| Subdomain | Type | Why it exists |
|-----------|------|---------------|

## Proposed Bounded Contexts
| Context | Responsibilities | Owns | Upstream/Downstream | Rationale |
|---------|------------------|------|---------------------|-----------|

## Ubiquitous Language
| Term | Meaning | Context |
|------|---------|---------|

## Aggregate Proposals
### Context: [Name]
| Aggregate | Purpose | Invariants | Key Commands | Key Events |
|-----------|---------|------------|--------------|------------|

## Risks and Open Questions
- Risk 1
specs/domain/domain-model.md

Include a Mermaid context map and per-context diagrams.

mermaid
graph TD
    Catalog[Catalog Context]
    Ordering[Ordering Context]
    Billing[Billing Context]
    Ordering -->|PublishedProduct| Catalog
    Ordering -->|ChargeRequested| Billing
mermaid
classDiagram
    class Order {
      +OrderId id
      +OrderStatus status
      +Money total
      place()
      cancel()
    }
    class OrderLine {
      +ProductId productId
      +Quantity quantity
      +Money unitPrice
    }
    class Money {
      +decimal amount
      +string currency
    }
    Order "1" *-- "many" OrderLine
    Order --> Money
specs/domain/database-model.md

Include Mermaid ERD diagrams and mapping notes.

mermaid
erDiagram
    ORDERS {
        uuid id PK
        varchar status
        decimal total_amount
        varchar total_currency
        timestamp created_at
    }
    ORDER_LINES {
        uuid id PK
        uuid order_id FK
        uuid product_id
        int quantity
        decimal unit_price_amount
        varchar unit_price_currency
    }
    ORDERS ||--o{ ORDER_LINES : contains

Quality Checklist

Before presenting the results:

  • Every FRD is mapped to one or more bounded contexts.
  • Ubiquitous language avoids technical jargon where a business term exists.
  • Every aggregate has explicit invariants and ownership.
  • Domain diagrams and database diagrams are Mermaid text, not images.
  • Cross-context relationships are explicit and named.
  • Brownfield outputs distinguish observed state from proposed state.
  • Assumptions and unresolved questions are called out, not hidden.

Mandatory Completion Checklist

The orchestrator MUST verify ALL of the following before marking ddd-modeling as complete:

  • specs/domain/proposals.md exists and includes bounded contexts, glossary, and aggregate proposals
  • specs/domain/domain-model.md exists and contains at least one Mermaid context map plus aggregate-level diagrams
  • specs/domain/database-model.md exists and contains a Mermaid ERD plus aggregate-to-persistence mapping notes
  • Every approved FRD is mapped to a bounded context
  • Every bounded context has explicit ownership and integration boundaries
  • For brownfield runs, observed constraints and proposed target boundaries are both documented

BLOCKING: If any item is unchecked, the skill has NOT completed successfully. The orchestrator must loop back and complete the missing items before using the model for planning or implementation.

Constraints

  • Preserve business language — do not substitute framework class names for domain concepts.
  • One aggregate root per transactional consistency boundary.
  • Do not introduce shared-database coupling across bounded contexts without explicit justification.
  • Label assumptions clearly when the available evidence is incomplete.
  • Keep proposals implementation-agnostic unless an existing ADR constrains the design.

Output State Updates

After generating the artifacts, update .spec2cloud/state.json with a domainModeling section when appropriate:

json
{
  "domainModeling": {
    "status": "complete",
    "artifacts": [
      "specs/domain/proposals.md",
      "specs/domain/domain-model.md",
      "specs/domain/database-model.md"
    ]
  }
}

Append to .spec2cloud/audit.log:

text
[ISO-timestamp] step=ddd-modeling action=artifacts-generated result=done

Handoff

After approval:

  1. Increment planning uses bounded contexts and aggregate boundaries to split work.
  2. Tech stack resolution uses persistence ownership and integration style to choose storage and messaging technologies.
  3. Contracts and implementation preserve the agreed context boundaries instead of collapsing everything into one model.

© EmeaAppGbb, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 1 other file (references) in .github/skills/ddd-modeling of EmeaAppGbb/spec2cloud.

  • SKILL.md
  • references/core-concepts.md

Open the folder on GitHubat commit 8e76618

Compare with similar skills

Ddd Modeling next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Ddd Modeling compared with similar skills
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Draw.io Diagram StudioAgents365-ai/drawio-skill10k—~2.4kAutomated safety check: NotesMIT
Pretty Mermaid Rendererimxv/Pretty-mermaid-skills1.5k—~2kAutomated safety check: PassMIT
Archify Diagram BuilderUnclecheng-li/AI_Animation1.4k2 repos~4.1kAutomated safety check: PassMIT

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Works with

Categories

Questions about Ddd Modeling

What does Ddd Modeling do?

Create Domain-Driven Design proposals from product specs or brownfield extraction outputs. Ddd Modeling is an agent skill from EmeaAppGbb/spec2cloud. Create Domain-Driven Design proposals from product specs or brownfield extraction outputs.

When should I use Ddd Modeling?

Ddd Modeling fits situations like: domain boundaries; data ownership need to be explicit before planning.

How do I install Ddd Modeling in Claude Code?

Run `npx skills add EmeaAppGbb/spec2cloud --skill ddd-modeling -a claude-code`. Or copy the skill folder (.github/skills/ddd-modeling in EmeaAppGbb/spec2cloud) into .claude/skills/ddd-modeling in your project. Claude Code loads it when a task matches its description.

How do I install Ddd Modeling in Codex?

Run `npx skills add EmeaAppGbb/spec2cloud --skill ddd-modeling -a codex`. Or copy the skill folder (.github/skills/ddd-modeling in EmeaAppGbb/spec2cloud) into .agents/skills/ddd-modeling in your project. Codex loads it when a task matches its description.

Can I use Ddd Modeling in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add EmeaAppGbb/spec2cloud --skill ddd-modeling -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/ddd-modeling, .gemini/skills/ddd-modeling, .github/skills/ddd-modeling and .opencode/skills/ddd-modeling in your project.

What does Ddd Modeling need to run?

SKILL.md names no scripts, command-line tools or credentials: Ddd Modeling is instructions for the agent only.

Does Ddd Modeling access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Ddd Modeling safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Ddd Modeling use?

Ddd Modeling is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Ddd Modeling use?

About 2.4k tokens (SKILL.md is roughly 9.6k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 318 tokens, read only when the agent opens those files.

What are the alternatives to Ddd Modeling?

Skills that share tags, products or a category with Ddd Modeling: Archify Diagrams (tt-a1i/archify, 79k stars), Diagram Design (cathrynlavery/diagram-design, 44k stars), Draw.io Diagram Studio (Agents365-ai/drawio-skill, 10k stars) and Pretty Mermaid Renderer (imxv/Pretty-mermaid-skills, 1.5k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Ddd Modeling?

EmeaAppGbb (a GitHub organization) maintains it in EmeaAppGbb/spec2cloud, which has 100 GitHub stars. The repository holds 39 skills in this directory. The repository was last updated on April 16, 2026.

Source: EmeaAppGbb/spec2cloud on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.