PostgreSQL MCP Server

Instructions

Implementation Reference

• src/index.js:310-335 (handler)

  The main handler function for the 'list_schemas' tool. It connects to the PostgreSQL database, queries the information_schema.schemata to list all schemas (excluding system schemas), formats the result as a bulleted list, and returns it in the MCP content format.

  async listSchemas() {
    const client = await this.connectToDatabase();
    
    try {
      const query = `
        SELECT schema_name 
        FROM information_schema.schemata 
        WHERE schema_name NOT IN ('information_schema', 'pg_catalog', 'pg_toast')
        ORDER BY schema_name;
      `;
      
      const result = await client.query(query);
      
      return {
        content: [
          {
            type: 'text',
            text: `Available schemas:\n\n` + 
                  result.rows.map(row => `• ${row.schema_name}`).join('\n'),
          },
        ],
      };
    } finally {
      await client.end();
    }
  }

• src/index.js:112-115 (schema)

  Input schema definition for the 'list_schemas' tool, specifying an empty object (no input parameters required).

  inputSchema: {
    type: 'object',
    properties: {},
  },

• src/index.js:109-116 (registration)

  Tool registration in the ListToolsRequestSchema response, defining the name, description, and input schema for 'list_schemas'.

  {
    name: 'list_schemas',
    description: 'List all schemas in the database',
    inputSchema: {
      type: 'object',
      properties: {},
    },
  },

• src/index.js:154-155 (registration)

  Dispatcher case in the CallToolRequestSchema handler that routes calls to the listSchemas() method.

  case 'list_schemas':
    return await this.listSchemas();