generate_er_diagram

Create Mermaid ER diagrams of database schemas using SingleStore MCP Server, enabling clear visualization of table relationships and structures for better database understanding.

Instructions

Generate a Mermaid ER diagram of the database schema

Input Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Implementation Reference

src/index.ts:1385-1448 (handler)

The handler function for 'generate_er_diagram' tool. It queries the database for tables and columns, fetches foreign key relationships (though not used), builds a Mermaid ER diagram with table schemas and adds some hardcoded relationships, then returns it as text content.

    case 'generate_er_diagram': {
      try {
        // Get all tables
        const [tables] = await conn.query(
          'SELECT TABLE_NAME FROM information_schema.TABLES WHERE TABLE_SCHEMA = DATABASE()'
        ) as [TableRowDataPacket[], mysql.FieldPacket[]];

        // Get foreign key relationships
        const [relationships] = await conn.query(
          `SELECT 
            TABLE_NAME,
            COLUMN_NAME,
            REFERENCED_TABLE_NAME,
            REFERENCED_COLUMN_NAME
          FROM information_schema.KEY_COLUMN_USAGE
          WHERE 
            TABLE_SCHEMA = DATABASE()
            AND REFERENCED_TABLE_NAME IS NOT NULL`
        ) as [mysql.RowDataPacket[], mysql.FieldPacket[]];

        // Start building Mermaid diagram
        let mermaidDiagram = 'erDiagram\n';

        // Add tables and their columns
        for (const table of tables) {
          const [columns] = await conn.query(
            'DESCRIBE ??',
            [table.TABLE_NAME]
          ) as [ColumnRowDataPacket[], mysql.FieldPacket[]];

          mermaidDiagram += `\n    ${table.TABLE_NAME} {\n`;
          for (const column of columns) {
            const fieldType = column.Type.split('(')[0];
            mermaidDiagram += `        ${fieldType} ${column.Field}${column.Key === 'PRI' ? ' PK' : ''}\n`;
          }
          mermaidDiagram += '    }\n';
        }

        // Add relationships
        mermaidDiagram += `
Documents ||--o{ Document_Embeddings : "has embeddings"
Documents ||--o{ Chunk_Metadata : "is chunked into"
Documents ||--o{ ProcessingStatus : "has status"
Document_Embeddings ||--o| Chunk_Metadata : "belongs to chunk"
Entities ||--o{ Relationships : "has relationships"
Entities ||--o{ Relationships : "is referenced by"
Documents ||--o{ Relationships : "contains"`;

        return {
          content: [
            {
              type: 'text',
              text: mermaidDiagram,
            },
          ],
        };
      } catch (error: unknown) {
        const err = error as Error;
        throw new McpError(
          ErrorCode.InternalError,
          `ER diagram generation error: ${err.message}`
        );
      }
    }

src/index.ts:1177-1184 (registration)
Registration of the 'generate_er_diagram' tool in the MCP server's list_tools response, including its name, description, and input schema (no required parameters).
```
{
  name: 'generate_er_diagram',
  description: 'Generate a Mermaid ER diagram of the database schema',
  inputSchema: {
    type: 'object',
    properties: {},
    required: [],
  },
```
src/index.ts:1181-1184 (schema)
Input schema definition for the generate_er_diagram tool (empty object, no parameters required).
```
  type: 'object',
  properties: {},
  required: [],
},
```

src/index.ts:136-144 (registration)

Secondary registration of the tool in the SSE HTTP server's cached tools list for list_tools requests.

{
  name: 'generate_er_diagram',
  description: 'Generate a Mermaid ER diagram of the database schema',
  inputSchema: {
    type: 'object',
    properties: {},
    required: [],
  },
},

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