To get the list of tables which can be included in reports, use the command report/get_report_tables:

svc=report/get_report_tables&params={}

[
	{
		"id":<uint>,		/* table ID */
		"n":<text>,		/* system table name */
		"l":<text>,		/* default table name */
		"t":<text>,		/* table type */
		"ct":<text>,		/* type of template in which this table can be used */
		"pt":<text>,		/* text parameters */
		"gt":<text>,		/* advanced grouping settings */
		"col":[			/* array of columns */
			{
				"n":<text>,	/* system column name */
				"l":<text>,	/* default column name */
				"sl":<text>,	/* list of column headers (if it is a statistics table) */
				"t":<text>,	/* column type */
				"f":<uint>	/* column flags (see below) */
			}
		]
	}
]

Report template types are described in the chapter Get templates data.