MyPos MCP

Instructions

Implementation Reference

• mcp_server.js:71-78 (handler)

  Inline handler function for the 'listarTablas' tool. It fetches the database schema using query_runner.getSchema() and returns a formatted list of table names.

  async () => {
    const schema = await query_runner.getSchema();
    return {
      content: [
        { type: 'text', text: 'Tablas:\n' + schema.map(t => `- ${t.name}`).join('\n') }
      ]
    };
  }

• mcp_server.js:64-79 (registration)

  Registration of the 'listarTablas' MCP tool using server.tool(), including description, empty input schema, and inline handler.

  server.tool(
    'listarTablas',
    'Sigue estas reglas para listar tablas:\n'
    + 'PROPÓSITO: Obtener una lista de todas las tablas en la base de datos.\n'
    + 'USO: Úsalo cuando necesites saber qué tablas existen.\n'
    + 'EJEMPLO: "Muestra las tablas disponibles."',
    {},
    async () => {
      const schema = await query_runner.getSchema();
      return {
        content: [
          { type: 'text', text: 'Tablas:\n' + schema.map(t => `- ${t.name}`).join('\n') }
        ]
      };
    }
  );

• mcp_server.js:70-70 (schema)

  Empty input schema (no parameters) for the 'listarTablas' tool.

  {},

• db_runners/QueryRunner.js:68-99 (helper)

  QueryRunner.getSchema() method: Retrieves list of tables and their columns using database-specific queries (SHOW TABLES for MySQL, information_schema for PostgreSQL). Called by the tool handler to get table names.

  async getSchema() {
    if (this.db_type === 'mysql') {
      const [tables] = await this.pool.execute("SHOW TABLES");
      const tableKey = Object.keys(tables[0])[0];
      return await Promise.all(tables.map(async tbl => {
        const tableName = tbl[tableKey];
        const [cols] = await this.pool.execute(`SHOW COLUMNS FROM \`${tableName}\``);
        return {
          name: tableName,
          columns: cols.map(c => ({ name: c.Field, type: c.Type }))
        };
      }));
    } else { // pg
      const res = await this.pool.query(`
        SELECT table_name
        FROM information_schema.tables
        WHERE table_schema = 'public' AND table_type='BASE TABLE'
      `);
      return await Promise.all(res.rows.map(async row => {
        const tname = row.table_name;
        const res2 = await this.pool.query(`
          SELECT column_name, data_type
          FROM information_schema.columns
          WHERE table_name = $1
        `, [tname]);
        return {
          name: tname,
          columns: res2.rows.map(c => ({ name: c.column_name, type: c.data_type }))
        };
      }));
    }
  }