A command that creates an entity relationship diagram in Mermaid format from Java entity files. An ERD is a visual map of database tables or entities and the relationships between them.

Generating a diagram for the whole application or a selected domain by reading Java entities and their JPA relationship annotations.

It turns JPA entity definitions into a readable view of the data model, making fields and one-to-one, one-to-many, and many-to-many relationships easier to inspect.

erd — Skill by demodev-lab

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods

npx agentmods add skills/demodev-lab/claude-code-plugin-demokit/erd

Any agent

npx skills add demodev-lab/claude-code-plugin-demokit --skill erd

Clone the repo

git clone --depth 1 https://github.com/demodev-lab/claude-code-plugin-demokit

Made for: Claude Code, Codex.

Or install demokit, the plugin that ships this one along with the rest of its 23 skills, 19 commands, 15 agents, 10 hooks.

Per session 47 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 622 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. Scan, not verified.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5	$0.00047	$0.00622
Opus 5	$0.00023	$0.00311
Sonnet 5	$0.00009	$0.00124
Haiku 4.5	$0.00005	$0.00062

Measured 2d ago against content hash de18b34d0811, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

erd scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/erd/SKILL.md · 76 lines

What it actually says

/erd - Entity Relationship Diagram

help

인자가 help이면 아래 도움말만 출력하고 실행을 중단한다:

/erd — Mermaid ERD 생성

사용법:
  /erd [domain]

파라미터:
  domain  대상 도메인 (선택, 기본 전체)

예시:
  /erd              — 전체 Entity ERD
  /erd User         — User 관련 ERD
  /erd all          — 전체 ERD (관계 포함)

관련 명령:
  /entity   — Entity 생성
  /crud     — CRUD 일괄 생성

실행 절차

Entity 파일 탐색:
- domain 인자 있으면 해당 도메인의 Entity만
- 미지정/all이면 전체 **/entity/*.java 탐색
- Glob과 Read로 모든 Entity 파일 수집
Entity 분석 (각 Entity 파일에서 추출):
- 클래스명, 테이블명 (@Table)
- 필드명, 타입, 어노테이션
- 관계 매핑: @OneToMany, @ManyToOne, @OneToOne, @ManyToMany
- 관계 대상 Entity 클래스
- @JoinColumn, mappedBy 속성

Mermaid ERD 생성:

erDiagram
    User {
        Long id PK
        String name
        String email UK
        LocalDateTime createdAt
    }
    Order {
        Long id PK
        Long userId FK
        OrderStatus status
        BigDecimal totalAmount
    }
    User ||--o{ Order : "has"

관계 표기 규칙:

JPA 어노테이션 Mermaid 관계 설명

@OneToOne ||--|| 1:1

@OneToMany ||--o{ 1:N

@ManyToOne }o--|| N:1

@ManyToMany }o--o{ N:M
출력 형식:
- Mermaid 코드 블록으로 출력
- Entity별 PK, FK, UK 표기
- Enum 타입은 타입명으로 표기
- BaseEntity 상속 필드 (createdAt, updatedAt) 포함
읽기 전용: 파일 수정 금지 (Read, Glob, Grep만 사용)

JPA 어노테이션	Mermaid 관계	설명
`@OneToOne`	`\|\|--\|\|`	1:1
`@OneToMany`	`\|\|--o{`	1:N
`@ManyToOne`	`}o--\|\|`	N:1
`@ManyToMany`	`}o--o{`	N:M

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

skill.yaml 84 B

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

2d ago First seen · 76 lines · 47 tokens per session scan A de18b34d0811

Subscribe to this mod's changes

erd is a skill published in the GitHub repository demodev-lab/claude-code-plugin-demokit (2 stars, last pushed 6mo ago), licensed MIT. It adds 47 tokens to every session and 622 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

Databases

prisma-upgrade-v7

Complete migration guide from Prisma ORM v6 to v7 covering all breaking changes. Use when upgrading Prisma versions, encountering v7 errors, or migrating existing projects. Triggers on "upgrade to prisma 7", "prisma 7 migration", "prisma-client generator", "driver adapter required".

nitrocloudofficial/nitrostack · 67 tokens

ddia-systems

Design data systems by understanding storage engines, replication, partitioning, transactions, and consistency models. Use when the user mentions "database choice", "which database should I use", "SQL or NoSQL", "replication lag", "partitioning strategy", "consistency vs availability", "stream processing", "ACID…

wondelai/skills · 138 tokens

sqlitecpp-update-sqlite

How to update the bundled SQLite3 amalgamation (sqlite3/sqlite3.c and sqlite3.h), the Meson wrap, README.md, and CHANGELOG.md. Use when upgrading SQLite, refreshing the vendored amalgamation, or bumping the sqlite3 wrap.

SRombauts/SQLiteCpp · 61 tokens

dsql

Build with Aurora DSQL — manage schemas, execute queries, handle migrations, diagnose query plans, diagnose cluster performance, load data, and develop applications with a serverless, distributed SQL database. Covers IAM auth, multi-tenant patterns, MySQL-to-DSQL and PostgreSQL-to-DSQL schema conversion, FK…

awslabs/agent-plugins · 227 tokens

mongodb-natural-language-querying

Generate read-only MongoDB queries (find) or aggregation pipelines using natural language, with collection schema context and sample documents. Use this skill whenever the user asks to write, create, or generate MongoDB queries, wants to filter/query/aggregate data in MongoDB, asks "how do I query...", needs help with…

mongodb/agent-skills · 162 tokens

sql-translate

Translate SQL queries between database dialects (Snowflake, BigQuery, PostgreSQL, MySQL, etc.).

AltimateAI/altimate-code · 26 tokens