Agent skill

M09 Domain

by fjrevoredo in fjrevoredo/mini-diarium

CRITICAL: Use for domain modeling. An agent skill from fjrevoredo/mini-diarium.

MITAuto-check passedDevelopment

Install M09 Domain

skills CLI

$ npx skills add fjrevoredo/mini-diarium --skill m09-domain -a claude-code

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

GitHub CLI

$ gh skill install fjrevoredo/mini-diarium m09-domain --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/fjrevoredo/mini-diarium.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/m09-domain .claude/skills/m09-domain && 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/

Paste into Claude Code

Install the "m09-domain" agent skill from https://github.com/fjrevoredo/mini-diarium/tree/master/.agents/skills/m09-domain into .claude/skills/m09-domain/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "m09-domain", then confirm the skill loads.

Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

$skill-installer

$skill-installer install https://github.com/fjrevoredo/mini-diarium/tree/master/.agents/skills/m09-domain

Type this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.

skills CLI

$ npx skills add fjrevoredo/mini-diarium --skill m09-domain -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install fjrevoredo/mini-diarium m09-domain --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/fjrevoredo/mini-diarium.git skills-src && mkdir -p .agents/skills && cp -r skills-src/.agents/skills/m09-domain .agents/skills/m09-domain && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "m09-domain" agent skill from https://github.com/fjrevoredo/mini-diarium/tree/master/.agents/skills/m09-domain into .agents/skills/m09-domain/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "m09-domain", then confirm the skill loads.

Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add fjrevoredo/mini-diarium --skill m09-domain -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install fjrevoredo/mini-diarium m09-domain --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/fjrevoredo/mini-diarium.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/.agents/skills/m09-domain .cursor/skills/m09-domain && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "m09-domain" agent skill from https://github.com/fjrevoredo/mini-diarium/tree/master/.agents/skills/m09-domain into .cursor/skills/m09-domain/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "m09-domain", then confirm the skill loads.

Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

gemini skills install

$ gemini skills install https://github.com/fjrevoredo/mini-diarium.git --path .agents/skills/m09-domain

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add fjrevoredo/mini-diarium --skill m09-domain -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install fjrevoredo/mini-diarium m09-domain --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/fjrevoredo/mini-diarium.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/.agents/skills/m09-domain .gemini/skills/m09-domain && rm -rf skills-src

Use ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.

Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/

Paste into Gemini CLI

Install the "m09-domain" agent skill from https://github.com/fjrevoredo/mini-diarium/tree/master/.agents/skills/m09-domain into .gemini/skills/m09-domain/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "m09-domain", then confirm the skill loads.

Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

GitHub CLI

$ gh skill install fjrevoredo/mini-diarium m09-domain

Installs for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).

skills CLI

$ npx skills add fjrevoredo/mini-diarium --skill m09-domain -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/fjrevoredo/mini-diarium.git skills-src && mkdir -p .github/skills && cp -r skills-src/.agents/skills/m09-domain .github/skills/m09-domain && rm -rf skills-src

Use ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.

GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/

Paste into GitHub Copilot

Install the "m09-domain" agent skill from https://github.com/fjrevoredo/mini-diarium/tree/master/.agents/skills/m09-domain into .github/skills/m09-domain/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "m09-domain", then confirm the skill loads.

GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add fjrevoredo/mini-diarium --skill m09-domain -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install fjrevoredo/mini-diarium m09-domain --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/fjrevoredo/mini-diarium.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/.agents/skills/m09-domain .opencode/skills/m09-domain && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "m09-domain" agent skill from https://github.com/fjrevoredo/mini-diarium/tree/master/.agents/skills/m09-domain into .opencode/skills/m09-domain/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "m09-domain", then confirm the skill loads.

OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

Facts

Skill name: m09-domain
GitHub stars: 308
Used in: 1 other repo
Token cost: ~1k tokens
SKILL.md length: 286 words
Files: 1
Skills in repo: 41
Repo updated: Oct 9, 2026
First seen: Oct 7, 2026
Licence: MIT

At a glance

CRITICAL: Use for domain modeling. An agent skill from fjrevoredo/mini-diarium.

Works in 3 steps: What's the concept's identity? → What invariants must hold? → Who owns this data?
Domain modeling
SKILL.md covers Core Question, Domain Concept → Rust Pattern, Thinking Prompt and Trace Up ↑, plus 5 more sections
Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

M09 Domain is an agent skill from fjrevoredo/mini-diarium. CRITICAL: Use for domain modeling. Triggers: domain model, DDD, domain-driven design, entity, value object, aggregate, repository pattern, business rules, validation, invariant, 领域模型, 领域驱动设计, 业务规则

Its SKILL.md is about 1k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Development, covering Domain-driven design. It works with Rust. The repository describes itself as: A local-only journal with serious encryption. Free, open source, and never touches the internet. The licence is MIT.

When your agent uses it

Domain modeling
Tasks that involve Domain-driven design

Example prompts

“/m09-domain”

Workflow steps

3 steps, taken from the first numbered list in SKILL.md.

What's the concept's identity?
What invariants must hold?
Who owns this data?

What it can do on your machine

Read from SKILL.md and the folder at commit eed457f. 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 rust).
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

M09 Domain loads about 1k tokens when it runs. Until then it costs about 52 tokens; SKILL.md has 286 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~52
When it runs · the whole SKILL.md, loaded when a task matches: ~1k

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 fjrevoredo/mini-diarium at commit eed457f, republished under its MIT licence (© fjrevoredo). 286 words, ~1,048 tokens.

Download SKILL.mdSave it as .claude/skills/m09-domain/SKILL.md (or your agent's skills folder).

name: m09-domain
description: CRITICAL: Use for domain modeling. Triggers: domain model, DDD, domain-driven design, entity, value object, aggregate, repository pattern, business rules, validation, invariant, 领域模型, 领域驱动设计, 业务规则
user-invocable: false

Domain Modeling

Layer 2: Design Choices

Core Question

What is this concept's role in the domain?

Before modeling in code, understand:

Is it an Entity (identity matters) or Value Object (interchangeable)?
What invariants must be maintained?
Where are the aggregate boundaries?

Domain Concept → Rust Pattern

Domain Concept	Rust Pattern	Ownership Implication
Entity	struct + Id	Owned, unique identity
Value Object	struct + Clone/Copy	Shareable, immutable
Aggregate Root	struct owns children	Clear ownership tree
Repository	trait	Abstracts persistence
Domain Event	enum	Captures state changes
Service	impl block / free fn	Stateless operations

Thinking Prompt

Before creating a domain type:

What's the concept's identity?
- Needs unique identity → Entity (Id field)
- Interchangeable by value → Value Object (Clone/Copy)
What invariants must hold?
- Always valid → private fields + validated constructor
- Transition rules → type state pattern
Who owns this data?
- Single owner (parent) → owned field
- Shared reference → Arc/Rc
- Weak reference → Weak

Trace Up ↑

To domain constraints (Layer 3):

"How should I model a Transaction?"
    ↑ Ask: What domain rules govern transactions?
    ↑ Check: domain-fintech (audit, precision requirements)
    ↑ Check: Business stakeholders (what invariants?)

Design Question	Trace To	Ask
Entity vs Value Object	domain-*	What makes two instances "the same"?
Aggregate boundaries	domain-*	What must be consistent together?
Validation rules	domain-*	What business rules apply?

Trace Down ↓

To implementation (Layer 1):

"Model as Entity"
    ↓ m01-ownership: Owned, unique
    ↓ m05-type-driven: Newtype for Id

"Model as Value Object"
    ↓ m01-ownership: Clone/Copy OK
    ↓ m05-type-driven: Validate at construction

"Model as Aggregate"
    ↓ m01-ownership: Parent owns children
    ↓ m02-resource: Consider Rc for shared within aggregate

Quick Reference

DDD Concept	Rust Pattern	Example
Value Object	Newtype	`struct Email(String);`
Entity	Struct + ID	`struct User { id: UserId, ... }`
Aggregate	Module boundary	`mod order { ... }`
Repository	Trait	`trait UserRepo { fn find(...) }`
Domain Event	Enum	`enum OrderEvent { Created, ... }`

Pattern Templates

Value Object

rust

struct Email(String);

impl Email {
    pub fn new(s: &str) -> Result<Self, ValidationError> {
        validate_email(s)?;
        Ok(Self(s.to_string()))
    }
}

Entity

rust

struct UserId(Uuid);

struct User {
    id: UserId,
    email: Email,
    // ... other fields
}

impl PartialEq for User {
    fn eq(&self, other: &Self) -> bool {
        self.id == other.id  // Identity equality
    }
}

Aggregate

rust

mod order {
    pub struct Order {
        id: OrderId,
        items: Vec<OrderItem>,  // Owned children
        // ...
    }

    impl Order {
        pub fn add_item(&mut self, item: OrderItem) {
            // Enforce aggregate invariants
        }
    }
}

Common Mistakes

Mistake	Why Wrong	Better
Primitive obsession	No type safety	Newtype wrappers
Public fields with invariants	Invariants violated	Private + accessor
Leaked aggregate internals	Broken encapsulation	Methods on root
String for semantic types	No validation	Validated newtype

When	See
Type-driven implementation	m05-type-driven
Ownership for aggregates	m01-ownership
Domain error handling	m13-domain-error
Specific domain rules	domain-*

Files

Just SKILL.md in .agents/skills/m09-domain of fjrevoredo/mini-diarium.

Open the folder on GitHubat commit eed457f

Used in 1 other repository

We found 1 copy of this SKILL.md (exact, near-identical or edited) in other folders, from 1 other GitHub owner. This page covers the copy in fjrevoredo/mini-diarium, which our catalogue first saw on October 7, 2026.

NeverSight/learn-skills.devdata/skills-md/actionbook/rust-skills/m09-domain

Compare with similar skills

M09 Domain 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.

M09 Domain compared with similar skills
Skill	Stars	Used in	Tokens	Auto-check	Licence	Repo updated
M09 Domain this skillfjrevoredo/mini-diarium	308	1 repos	~1k	Automated safety check: Pass	MIT	today
Rust Contract Domain Modelingaxone-protocol/contracts	123	—	~678	Automated safety check: Pass	BSD-3-Clause	13 days ago
Build Teaql Appteaql/teaql-agent-kit	2.8k	—	~4.6k	Automated safety check: Pass	MIT	12 days ago
Domain Modelingfossasia/eventyay-interpretation	1.6k	31 repos	~821	Automated safety check: Pass	Apache-2.0	4 days ago
Migrate Core Code to Submodulestinyhumansai/openhuman	42k	—	~2.6k	Automated safety check: Pass	GPL-3.0	today
OpenLogi macOS Permissions TriageAprilNEA/OpenLogi	23k	—	~2.5k	Automated safety check: Notes	Apache-2.0	today

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Questions about M09 Domain

What does M09 Domain do?

CRITICAL: Use for domain modeling. An agent skill from fjrevoredo/mini-diarium. M09 Domain is an agent skill from fjrevoredo/mini-diarium. CRITICAL: Use for domain modeling.

When should I use M09 Domain?

M09 Domain fits situations like: domain modeling; tasks that involve Domain-driven design.

How do I install M09 Domain in Claude Code?

Run `npx skills add fjrevoredo/mini-diarium --skill m09-domain -a claude-code`. Or copy the skill folder (.agents/skills/m09-domain in fjrevoredo/mini-diarium) into .claude/skills/m09-domain in your project. Claude Code loads it when a task matches its description.

How do I install M09 Domain in Codex?

Run `npx skills add fjrevoredo/mini-diarium --skill m09-domain -a codex`. Or copy the skill folder (.agents/skills/m09-domain in fjrevoredo/mini-diarium) into .agents/skills/m09-domain in your project. Codex loads it when a task matches its description.

Can I use M09 Domain 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 fjrevoredo/mini-diarium --skill m09-domain -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/m09-domain, .gemini/skills/m09-domain, .github/skills/m09-domain and .opencode/skills/m09-domain in your project.

What does M09 Domain need to run?

SKILL.md names no scripts, command-line tools or credentials: M09 Domain is instructions for the agent only.

Does M09 Domain 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 M09 Domain 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 M09 Domain use?

M09 Domain 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 M09 Domain use?

About 1k tokens (SKILL.md is roughly 4.2k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to M09 Domain?

Skills that share tags, products or a category with M09 Domain: Rust Contract Domain Modeling (axone-protocol/contracts, 123 stars), Build Teaql App (teaql/teaql-agent-kit, 2.8k stars), Domain Modeling (fossasia/eventyay-interpretation, 1.6k stars) and Migrate Core Code to Submodules (tinyhumansai/openhuman, 42k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains M09 Domain?

fjrevoredo (a GitHub user) maintains it in fjrevoredo/mini-diarium, which has 308 GitHub stars. The repository holds 41 skills in this directory. The repository was last updated on October 9, 2026.

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

Install M09 Domain

Facts

At a glance

What it does

When your agent uses it

Example prompts

Workflow steps

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

Domain Modeling

Core Question

Domain Concept → Rust Pattern

Thinking Prompt

Trace Up ↑

Trace Down ↓

Quick Reference

Pattern Templates

Value Object

Entity

Aggregate

Common Mistakes

Related Skills

Files

Used in 1 other repository

Compare with similar skills

Similar skills

More from fjrevoredo/mini-diarium

Related

Questions about M09 Domain