@arvoretech/db-diagram-mcp

MCP Server that generates Mermaid ER diagrams from SQL DDL.

Tools

| Tool | Description | |------|-------------| | generate_erd | Full ER diagram from DDL. Optionally filter to specific tables. | | generate_domain_map | BFS from an entry table, showing all related tables within N hops. | | explain_table | Column details, incoming/outgoing FKs, and a mini neighborhood diagram. | | trace_flow | Find relationship paths between two tables with a connecting diagram. |

Usage

All tools accept DDL as input (no database connection required).

{
  "ddl": "CREATE TABLE users (...); CREATE TABLE posts (...);",
  "tables": ["users", "posts"],
  "title": "User Domain"
}

Output

All diagram output is Mermaid syntax, ready to render in GitHub, Notion, or any Mermaid-compatible viewer.

Running

# stdio transport (for MCP clients)
npx @arvoretech/db-diagram-mcp

# or via pnpm in this monorepo
pnpm --filter @arvoretech/db-diagram-mcp dev

Composable Pattern

This MCP doesn't connect to databases directly. Feed it DDL from your existing database MCPs:

1. Use mysql-mcp or postgresql-mcp to get schema (SHOW CREATE TABLE or pg_dump --schema-only)
2. Pass the DDL output to generate_erd or other tools
3. Get Mermaid diagrams back